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. 2022 Nov 29;17(11):e0278193. doi: 10.1371/journal.pone.0278193

Pregnancy outcomes of immigrant women living in Korea: A population-based study

Geum Joon Cho 1, Ho Yeon Kim 1, Hyun Sun Ko 2, Hae Joong Cho 3, Seong Yeon Hong 4, Eunjin Noh 5, Young Ju Jeong 6,*
Editor: Rubeena Zakar7
PMCID: PMC9707740  PMID: 36445896

Abstract

Although there is a high rate of pregnant immigrant women in Korea, little is known regarding their pregnancy outcomes. The aim of this study was to evaluate the pregnancy outcomes of immigrant women in Korea. Data for all pregnant women who gave birth between January 1, 2007 and December 31, 2016 were obtained using the Health Insurance Review and Assessment Service Database. Pregnant women were divided into two groups: Korean and immigrant women. The main outcome measures were adverse pregnancy outcomes including gestational diabetes of mellitus, preeclampsia, cesarean section, placental abrnomalities, and postpartum hemorrhage. The odds of gestational diabetes mellitus, preeclampsia, cesarean section, placental previa, placental abruptio, and postpartum hemorrhage was compared between the two groups. Among 4,439,778 pregnant women who gave birth during the study period, 168,940 (3.8%) were immigrant women. The odds of gestational diabetes mellitus (adjusted OR: 1.24; 95% CI: 1.21, 1.28), and cesarean section (adjusted OR: 1.26; 95% CI: 1.25–1.28)were higher in immigrant women than in Korean women, but the odds of preeclampsia (adjusted OR: 0.84; 95% CI: 0.81–0.86) and postpartum hemorrhage (adjusted OR 0.96, 95% CI 0.94–0.97) was lower in immigrant women than in Korean women. Immigrant women had different pregnancy outcomes. Pregnancy and postpartum management that reflects these characteristics will be necessary for immigrant women.

Introduction

South Korea has been suffered from low birth rate predominantly due to fast urbanization that the total fertility or birth rate is below 1 in 2021(Korea Statistical Information Service[KOSIS], 2021). Consequently, this low birth rate has further slowed the population growth and has rapidly transitioned to an aged society than any other country in the world. To overcome this social phenomenon, the Korean government has implemented more favorable environment for childbearing and encouraged interracial marriages as a method of securing a labor force [1, 2] Therefore, interracial marriages in Korea are common, particularly in the past two decades due to “wife shortages” [3]. In 2018, 22,698 interracial marriages were registered, with 16,608 foreign wives and 6,090 foreign husbands. A total of 257,622 spouses were recorded; therefore, 8.81% of all marriages in Korea were interracial in 2018 [4].

After immigration various factors originating from different cultures, economy and communication may lead to problems with health outcomes of foreign wives [5]. In reproductive health, many obstetric investigations across different countries have limited adjustment for ethnicity, compared to native women, immigrant women have an increased risk of preterm birth, low birth weight and cesarean section [6–9]. In addition, it has been reported that immigrants in countries of resettlement have a greater risk of gestational diabetes mellitus (GDM) than women in receiving countries [10]. Thus, influxes of migrant women of childbearing age to receiving countries have made their perinatal health status a key priority for many governments [9].

Adverse pregnancy-related outcomes including hypertensive disorders, GDM, small for gestational age and postpartum hemorrhage have been steadily increasing especially due to advanced maternal age and higher body mass index(BMI) in South Korea [11–13]. Perinatal outcomes are influenced by not only maternal age and BMI but also smoking and alcohol consumption and further influences of racial and ethnic disparities have been documented. Evidences have shown increasing trends of interracial marriages in South Korea and this phenomenon may be related to adverse pregnancy outcomes which can lead to enormous burden on society.

We previously investigated birth outcomes using data obtained from the National Birth Registry of the Korean Statistical Office and found that the birthweight was lower, and that the risk of low birth weight was increased in foreign pregnant women compared to Korean pregnant women [14]. However, data obtained from the National Birth Registry of the Korean Statistical Office has a limitation in evaluating pregnancy outcomes, such as preeclampsia and GDM, due to lack of data. The aim of this study was to evaluate the pregnancy outcomes of immigrant women in Korea.

Materials and methods

Study design

Using the HIRA Database, we identified all pregnant women who gave birth between January 1, 2007 and December 31, 2016. Maternal ethnicity was identified and divided into two categories: Korean pregnant women and immigrant pregnant women.

Data characteristics

The study data were collected from the Health Insurance Review and Assessment Service (HIRA) Database for 2007–2016. In Korea, 97% of the population is required to enroll in the Korea National Health Insurance (KNHI) program, with the exception of the remaining 3% of the population who are treated under the Medical Aid Program. Healthcare providers are required by health insurance policies to allow the HIRA to review medical costs. Thus, the HIRA database contains information on all claims for approximately 50 million Koreans, and nearly all information regarding the incidence of disease can be obtained from this centralized database, with the exception of procedures that are not covered by insurance, such as cosmetic surgery. According to the Act on the Protection of Personal Information Maintained by Public Agencies, the HIRA prepares the claims data by concealing individual identities. The HIRA database we received included unidentifiable codes that represented individuals, together with age, diagnosis, and a list of prescribed procedures.

Ethical consideration

This study was approved by the Institutional Review Committees of Korea University Guro Hospital (KUGH17273). The informed consent was waived by this IRB because the HIRA database does not include individual identities and because of retrospective nature of this study. This study comprises of third-party data therefore authors cannot share data nor legally distribute.

Dataset and outcomes

Using the International Classification of Diseases, Tenth Revision (ICD-10), diagnoses of preeclampsia, GDM, placental previa, placental abruptio, and postpartum hemorrhage(PPH) were obtained from the KNHI Claims Database. Parity, and the rate of cesarean section, induction of labor vacuum delivery, uterine arterial embolization (UAE), and peripartum hysterectomy (PH) were also identified using the presence of a Korea Medical Insurance electronic data interchange (EDI) code.

Main outcome of this study were adverse pregnancy outcomes including GDM, preeclampsia, cesarean section, induction of labor, vacuum delivery, placenta previa, placenta abruption, PPH, peripartum hysterectomy and UAE. Age, parity and CCI were adjusted for multiple logistic regression analysis.

Covariates

The Charlson Comorbidity Index (CCI) was identified using ICD-10 codes in order to adjust for pre-pregnancy factors. The CCI has been known to be a useful and most widely used tool to measure comorbid disease status including cardiovascular diseases, diabetes, malignancies and autoimmune diseases or casemix in health care databases that the higher the score the more comorbid conditions are present [15]. Acute myocardial infarction, congestive heart failure, peripheral vascular disease, cerebral vascular accident, dementia, pulmonary disease, connective tissue disorder, peptic ulcer, liver disease, diabetes, diabetes complications, paraplegia, renal disease, cancer, metastatic cancer, severe liver disease, and HIV were analyzed in this study. The CCI score was categorized as 0, 1, 2, 3, and ≥ 4 [16].

Statistical analysis

The Student’s t-test was used to compare continuous variables between Korean and immigrant pregnant women, while the chi-square test was used to compare categorical variables. A Secular trend in the rate of immigrant pregnant women was determined and compared across years using the χ2 Cochran-Armitage test. Multivariable logistic regression analysis was used to estimate the adjusted odds ratio (OR) and the 95% confidence intervals (CIs) for adverse pregnancy outcomes. The model was run stepwise. Statistical analyses were performed using SAS for Windows, version 9.4 (SAS Inc., Cary, NC, USA).

Result

Among 4,439,778 pregnant women who gave birth during the study period, 168,940 (3.8%) were immigrant women. The rate of immigrant women increased from 2.98% in 2007 to 4.53% in 2016 (p-value for trend < 0.01) (Fig 1).

Fig 1. Secular trends of the rate of immigrant pregnancy women in Korea.

Fig 1

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Table 1 shows the basic characteristics of the study population according to maternal ethnicity. Foreign women were younger and more primiparous than Korean women, and tended to have lower CCI score than Korean women.

Table 1. Basic characteristics of the study population.

Korean women (n = 4,270,838) Immigrant women (n = 168,940) P-value
Age (years) 31.08 ± 4.07 27.20 ± 5.30 < 0.01a
Primiparity (n, %) 2,210,063 (51.75) 111,787 (66.17) < 0.01b
CCI score (n, %) < 0.01b
    0 20,93,245 (49.01) 129,849 (76.86)
    1 1,200,144 (28.10) 28,843 (17.07)
    2 613,132 (14.36) 7,557 (4.47)
    3 240,100 (5.62) 1,906 (1.13)
    ≥4 124,217 (2.91) 785 (0.46)
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Values are expressed as mean (SD) or number, %.

a p-value associated with student t-test

b p-value associated with chi-square test

Abbreviations: CCI: Charlson Comorbidity Index

CCI included acute myocardial infarction, congestive heart failure, peripheral vascular disease, cerebral vascular accident, dementia, pulmonary disease, connective tissue disorder, peptic ulcer, liver disease, diabetes, diabetes complications, paraplegia, renal disease, cancer, metastatic cancer, severe liver disease, and HIV.

Table 2 shows the pregnancy outcomes of the study population according to maternal ethnicity. Foreign women had a lower prevalence of preeclampsia than Korean women. The rate of cesarean section (CS), induction was lower in foreign women than Korean women. The incidence of placenta abruption, placenta previa, PPH, PH, and UAE were lower in immigrant women than Korean women.

Table 2. The pregnancy outcomes of the study population.

Korean women (n = 4,270,838) Immigrant women (n = 168,940) P-value
GDM (n, %) 182,874 (4.28) 5,526 (3.27) < 0.01
Preeclampsia (n, %) 166,202 (3.89) 4,871 (2.88) < 0.01
Cesarean section (n, %) 1,613,028 (37.77) 61,036 (36,13) < 0.01
Induction (n, %) 995,220 (23.30) 35,769 (21.17) < 0.01
Vacuum delivery (n, %) 252,463 (5.91) 13,373 (7.92) < 0.01
Placental previa (n, %) 43,480 (1.02) 1,248 (0.74) < 0.01
Placental abruption (n, %) 15,232 (0.36) 502 (0.30) < 0.01
PPH (n, %) 376,800 (8.82) 13,610 (8.06) < 0.01
Peripartum hysterectomy (n, %) 4,734 (0.11) 139 (0.08) < 0.01
UAE (n, %) 6,126 (0.14) 181 (0.11) < 0.01
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Values are expressed as number,%

P-value are all associated with chi-square test.

Abbreviations: GDM: Gestational diabetes mellitus, PPH: Postpartum hemorrhage, PH: Peripartum hysterectomy, UAE: Uterine arterial embolization

Table 3 represents the odds of adverse pregnancy outcomes by maternal ethnicity. The odds of GDM, preeclampsia, CS, placental abruption, placental previa, PPH, PH, and UAE was lower in foreign women than Korean women. However, after adjustment for age, parity, and CCI, the odds of GDM (adjusted OR: 1.24; 95% CI: 1.21, 1.28), and CS (adjusted OR: 1.26; 95% CI: 1.25–1.28), were higher in immigrant women than Korean women, but the odds of preeclampsia (adjusted OR: 0.84; 95% CI: 0.81–0.86) and PPH (adjusted OR: 0.96; 95% CI: 0.94–0.97) was lower. The odds of placental abruption (adjusted OR: 0.96; 95% CI: 0.88–1.05), PH (adjusted OR: 1.17; 95% CI: 0.98–1.38), and UAE (adjusted OR: 1.07; 95% CI: 0.92–1.24) was not different between the two groups after adjustment for age, parity, and CCI.

Table 3. Odds ratio and 95% confidence intervals of adverse pregnancy outcomes of 155 immigrant women.

Unadjusted ORs (95% CI) Model 1 Model 2 Model 3
GDM 0.76 (0.74, 0.78) 1.06 (1.04, 1.09) 1.06 (1.03, 1.09) 1.24 (1.21, 1.28)
Preeclampsia 0.73 (0.71, 0.76) 0.80 (0.78, 0.83) 0.80 (0.77, 0.82) 0.84 (0.81, 0.86)
Cesarean section 0.93 (0.92, 0.94) 1.23 (1.22, 1.24) 1.23 (1.21, 1.24) 1.26 (1.25, 1.28)
Induction 0.88 (0.87, 0.90) 0.76 (0.75 0.77) 0.76 (0.75, 0.77) 0.77 (0.76, 0.78)
Vacuum delivery 1.37 (1.35, 1.39) 1.07 (1.05, 1.09) 1.08 (1.06, 1.10) 1.07 (1.05, 1.09)
Placental previa 0.72 (0.68, 0.77) 1.05 (0.99, 1.11) 1.02 (0.97, 1.08) 1.06 (1.00, 1.12)
Placental abruption 0.83 (0.76, 0.91) 0.95 (0.87, 1.04) 0.94 (0.86, 1.03) 0.96 (0.88, 1.05)
PPH 0.91 (0.89, 0.92) 0.93 (0.91, 0.95) 0.93 (0.91, 0.94) 0.96 (0.94, 0.97)
PH 0.74 (0.63, 0.88) 1.15 (0.98, 1.37) 1.19 (1.00, 1.41) 1.17 (0.98, 1.38)
UAE 0.75 (0.64, 0.87) 1.04 (0.89, 1.20) 1.02 (0.88, 1.18) 1.07 (0.92, 1.24)
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Abbreviations: GDM: Gestational diabetes mellitus, PPH: Postpartum hemorrhage, PH: Peripartum hysterectomy, UAE: Uterine arterial embolization

Model 1 is adjusted for age.

Model 2 is adjusted for age and parity.

Model 3 is adjusted for age, parity, and CCI

Discussion

In this study, we evaluated pregnancy outcomes according to maternal ethnicity and found differences in pregnancy outcomes. Immigrant women were protected against having preeclampsia and PPH and higher risk of GDM, and CS compared to Korean women after adjustment for age, parity, and CCI.

The international research collaboration Reproductive Outcomes And Migration reviewed published studies and found that immigrants in countries of resettlement have a greater risk of GDM than do women in receiving countries [10]. Similarly, we found that immigrant women had a lower prevalence but a higher risk of GDM than did Korean women after adjustment for confounding factors. Various explanations are possible for these associations. First, there was considerable heterogeneity in the prevalence of GDM in Asia, with a relatively low prevalence in Korea [17]. Therefore, foreigners may have a relatively high incidence of GDM because they show prevalence based on the characteristics of their home countries. Second, it has been reported that pre-pregnancy and pregnancy dietary patterns are associated with the development of GDM [18, 19]. Dietary acculturation is one of the cultural elements into which female immigrants first assimilate, while living away from their home country [20, 21]. Therefore, there is a possibility that the risk of GDM increased through changes in dietary pattern after moving to Korea. However, due to the lack of relevant data, further research will be needed to determine the exact cause for these differences.

GDM is associated with adverse pregnancy outcomes, including gestational hypertensive disorders, fetal macrosomia, and cesarean delivery, [22] as well as an increased risk of developing type 2 DM after delivery [23]. Therefore, there is a need for systematic and continuous management of GDM both during pregnancy and after delivery. However, it has been reported that before the diagnosis of GDM, knowledge and awareness of diabetes were low in immigrant women. Moreover, the dietary advice that was received was seen to be challenging in the context of culturally different food habits; consequently, managing diet after diagnosis proved difficult [24]. Thus, as these groups may be vulnerable to management of GDM during pregnancy and postpartum, efforts will be needed to manage them appropriately.

In this study, the cesarean section rate was lower in immigrant women than in Korean women, but after adjustment for age, parity and CCI, the odds for cesarean section was higher in immigrant women. Immigrant women were younger than Korean women therefore age might be a factor which influence the lower rate of CS before adjustment. These results are consistent with those of a previous study reporting that cesarean rates between migrants and non-migrants differed in 69% of studies [9]. Thus, it is interesting finding, and although the exact cause is unknown, the increased cesarean rates for immigrant women can probably be explained by multiple factors. First, it may be due to the characteristics of immigrant women; for example, Asian women, particularly those from Southeast Asia, are generally shorter than Korean women [25]. Indeed, it has been well reported that maternal height exerts an effect on the risk of CS, with increasing risk of CS with decreasing maternal height [26]. Moreover, the increased rates for immigrant women can probably be explained by other factors such as social and health determinants, communication barriers, and cultural preferences [9].

Consistent with results of other studies, [27] the risk of preeclampsia was lower in immigrant women than in Korean women. Moreover, the association with PPH is inconsistent across studies, with some studies reporting an increased risk in immigrants, [28, 29] while others did not [30]. In this study, the risk of PPH was lower in immigrant women, but there was no significant difference in the occurrence of PH and UAE between the two groups.

In this study, we adjusted for CCI as a covariant to correct the pre-pregnancy health status and found that immigrant women had a lower CCI score than Korean women. However, it is unclear whether these results are due to the health of the immigrant women or the lack of information on medical records in Korea after the migration. Thus, further studies are needed to evaluate pregnancy outcomes according to maternal ethnicity considering pre-pregnancy health status.

This is one of the largest population based study on pregnancy outcome of interracial marriages without missing data. However some limitations should be acknowledged when interpreting our findings. As our study was confined to claims data on reimbursement for a medical service, we could not determine the effect on pregnancy outcomes according to the exact maternal nationality. Therefore, immigrant women may be mixed with Asians and Caucasians, and there may be differences in pregnancy outcomes among them. As such, future studies that reflect the exact nationality will be needed. Second, although the HIRA database comprises representative data of the whole country, it lacks information on uninsured medical claims, employment status, educational level as well as clinical information before the period we studied. In particular, it was difficult to obtain previous medical histories of migrant women in their previous country. Moreover, there are no reported characteristics on the women’s partners. Lastly, there appears to be no missing data since we could assess to data of women who had deliveries covered by national health insurance system.

Our study with large population data demonstrated different pregnancy outcomes of immigrant women. Increased risk of GDM, and CS were showed after adjusting maternal age, parity and CCI. This result will help clinicians to consider different pregnancy outcomes when they meet immigrant women. Eventually, predicting and preparing for adverse pregnancy outcome in advance will contribute to improving pregnancy outcomes.

Abbreviations

GDM

gestational diabetes

HIRA

Health Insurance Review and Assessment Service

KNHI

Korea National Health Insurance

UAE

uterine arterial embolization

CS

Cesarean section

PH

peripartum hysterectomy

PPH

postpartum hemorrhage

CCI

Charlson Comorbidity Index

Data Availability

The access to raw data of the Korean Health Insurance Review and Assessment (HIRA) service is regulated by the Rules for Data Exploration and Utilization of the HIRA. Data are available from the Health Insurance Review and Assessment Service database for researchers who meet the criteria for access to confidential data only after receiving an approval for the data use from the data access committee of the HIRA. HIRA data can be requested through its website (http://opendata.hira.or.kr).

Funding Statement

This research was supported by the Korean society of Maternal Fetal Medicine Research Fund. (grant no. KSMSM-2017-001) The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

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3 Sep 2021

PONE-D-21-06981

Pregnancy outcomes of immigrant women living in Korea: A population-based study

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This article addresses an actual problem: the pregnancy outcomes among immigrant women in Korea. There are a number of issues with the methods and analysis that need to be clarified/addressed. Below are more specific comments by section:

Abstract:

Since you are calculating the OR, you should consider replacing “risk” by “odds”.

Introduction

I do not see what does the information about interracial marriages adds in the section.

The authors take a rather narrow view of data publication,

Materials & Methods / Datasets and outcomes

You are not describing from where you are taking the variable age from.

Results section

This section needs to be improved. The variables selected for describing the study population are not exhaustive. If available, authors could also present information on employment status and educational level, previous c-section, Hypertension. Diabetes, for basic characteristics and potential risk factors. If you do not have information on these previous risk factors, you might want to mention it as a limitation.

Information regarding the % of missing data on each variable (you refer to this in the discussion section) could be useful

Table 1 includes information about outcomes that shouldn’t be described here. (GBD, preeclampsia. CS, induction etc)

When describing table 2 authors should refer as odds in state of risk. You might want to include information on low birth weigh and/or preterm birth since part of your background information includes those outcomes.

Discussion section

The first paragraph is confusing. Which are you main findings?

Line 179. You are including new information (birthweight) that was not mention on the results section.

Try to stress what your data adds to the existing body of evidence

Reviewer #2: The authors made a great presentation of the study findings - clearly linking the problem, aims, research questions, methodology, analysis results/findings, discussions, conclusions, and recommendations. Also, study clearly demonstrated associating factors with pregnancy outcomes in both groups. However, authors could provide more details in explanation to help the audience understand how caesarean section rate affects pregnancy outcome among immigrant women and state which specific cofounding factors affected (increased) caesarean section among immigrant women [line 176 & 177].

Over all, I think this is a technically sound and well documented study with details clearly stated findings and recommendations. Authors should state in the conclusion who (government, health workers, policy makers,…) is responsible for implementing effective pregnancy and postpartum management change/intervention for immigrant women [line 206 & 207] to enhance social change.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Gabriel Adebe PhD

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

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PLoS One. 2022 Nov 29;17(11):e0278193. doi: 10.1371/journal.pone.0278193.r002

Author response to Decision Letter 0

23 Dec 2021

Reviewer #1: This article addresses an actual problem: the pregnancy outcomes among immigrant women in Korea. There are a number of issues with the methods and analysis that need to be clarified/addressed. Below are more specific comments by section:

Abstract:

Since you are calculating the OR, you should consider replacing “risk” by “odds”.

Response: As you have pointed out, we wrote “odds” instead of “risk” as suggested.

Introduction

I do not see what does the information about interracial marriages adds in the section.

The authors take a rather narrow view of data publication,

Response: We fully agree with your suggestion. We corrected the introduction as follows (Line 65-75)

Preterm birth and low birth weight are serious adverse pregnancy outcomes. They are not only related to infant morbidity and mortality but also increase risk for chronic diseases such as cardiovascular diseases and metabolic syndrome during lifetime[1]. Several biological risk factors have been identified such as maternal age, body mass index and smoking and alcohol consumption. Further influences of racial and ethnic disparities have been documented. Although, many obstetric investigations across different countries have limited adjustment for ethnicity, compared to native women, immigrant women have an increased risk of preterm birth, low birth weight and cesarean section.[1,2, 4,5] It has been reported that immigrants in countries of resettlement have a greater risk of gestational diabetes mellitus (GDM) than women in receiving countries.[3] Thus, influxes of migrant women of childbearing age to receiving countries have made their perinatal health status a key priority for many governments.[5]

Materials & Methods / Datasets and outcomes

You are not describing from where you are taking the variable age from.

Response: We added “HIRA” in this sentence (Line 94-95) as following: “The HIRA database we received included unidentifiable codes that represented individuals, together with age, diagnosis, and a list of prescribed procedures.”

Results section

This section needs to be improved. The variables selected for describing the study population are not exhaustive. If available, authors could also present information on employment status and educational level, previous c-section, Hypertension. Diabetes, for basic characteristics and potential risk factors. If you do not have information on these previous risk factors, you might want to mention it as a limitation.

Response: We included limited information obtained from HIRA database and wrote limitation of certain risk factors (Line 201-205) in discussion. “Second, although the HIRA database comprises representative data of the whole country, it lacks information on uninsured medical claims, employment status, educational level as well as clinical information before the period we studied. In particular, migrant women do not know their past history in their previous country. ”

Information regarding the % of missing data on each variable (you refer to this in the discussion section) could be useful

Response: The strength of our study is that there is no missing data in HIRA database. We added this comment on page 13, line 206-207.

Table 1 includes information about outcomes that shouldn’t be described here. (GBD, preeclampsia. CS, induction etc)

Response: We reorganized table 1 into table 1 which includes basic characteristics and table 2 which includes pregnancy outcome.

When describing table 2 authors should refer as odds in state of risk. You might want to include information on low birth weigh and/or preterm birth since part of your background information includes those outcomes.

Response: We changed the risk to odds in Line 134-142.

Discussion section

The first paragraph is confusing. Which are you main findings?

Response: We clarified the first paragraph of discussion as follows.

“Immigrant women had a lower prevalence of preeclampsia and PPH and higher prevalence of GDM, CS and placenta previa compared to Korean women after adjustment for age, parity, and CCI.”

Line 179. You are including new information (birthweight) that was not mention on the results section.

Response: We deleted this irrelevant sentence. “In line with this, we previously reported that the birthweight was lower for the children of foreign women than for those of Korean women.”

Try to stress what your data adds to the existing body of evidence

Response: Our study with large population data demonstrated different pregnancy outcomes of immigrant women. Increased risk of GDM, CS and placenta previa were showed after adjusting maternal age, parity and CCI. This result will help clinicians to consider different pregnancy outcomes when they meet immigrant women. Eventually, predicting and preparing for adverse pregnancy outcome in advance will contribute to improving pregnancy outcomes.

 

Reviewer #2: The authors made a great presentation of the study findings - clearly linking the problem, aims, research questions, methodology, analysis results/findings, discussions, conclusions, and recommendations. Also, study clearly demonstrated associating factors with pregnancy outcomes in both groups. However, authors could provide more details in explanation to help the audience understand how caesarean section rate affects pregnancy outcome among immigrant women and state which specific cofounding factors affected (increased) caesarean section among immigrant women [line 176 & 177].

Response: We added following statement in Line 176-179. “In this study, the cesarean section rate was lower in immigrant women than in Korean women, but after adjustment for age, parity and CCI, the risk for cesarean section was higher in immigrant women. Immigrant women were younger than Korean women therefore age might be a factor which influences the lower rate of CS before adjustment.”

Over all, I think this is a technically sound and well documented study with details clearly stated findings and recommendations. Authors should state in the conclusion who (government, health workers, policy makers,…) is responsible for implementing effective pregnancy and postpartum management change/intervention for immigrant women [line 206 & 207] to enhance social change.

Response: We added following statement in the last paragraph of this manuscript(Line 207-209). “These characteristics should be reflected in Korean medical system to enhance social changes and effective pregnancy and postpartum management by healthcare providers will be necessary for immigrant women.”

Attachment

Submitted filename: response to reviewer plos one.docx

Click here for additional data file. (17.6KB, docx)

Decision Letter 1

Rubeena Zakar

28 Mar 2022

PONE-D-21-06981R1Pregnancy outcomes of immigrant women living in Korea: A population-based studyPLOS ONE

Dear Dr. Ju Jeong

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by 12th May 2022. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Rubeena Zakar, Ph.D

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The paper needs language editing. Consider a language revision.

When explaining The Charlson Comorbidity Index it would be useful to explain if the higher the score the more comorbid conditions are present (line 110)

From line 135 to 140 you described table 1, but in the middle of the paragraph there is information related to table 2 (The cesarean section (CS) rate was lower in foreign women than Korean women. The incidence of placental abruption, placental previa, PPH, PH, and UAE

were lower in immigrant women than Korean women.) that information was repeated in line 150.

Table 2. you included: Values are expressed as mean (SD) or %. But there are not values expressed as mean and SD

Table 3. should be named: Odds ratio and 95% confidence intervals of adverse pregnancy out 155 comes of immigrant women instead of Odds ratio and 95% confidence intervals of the risk of adverse pregnancy out 155 comes of immigrant women

This sentence is confusing:

In particular, migrant women do not know their past history in their previous country

Which is their past history they don’t know?

In table 1 it says “Primparity” check spelling

Line 187: it says risks, it should say odds

190. I still see the sentences: In line with this, we previously reported that the birthweight was lower for the children of foreign women than for those of Korean women.[11]

In this sense: I asked you before, Try to stress what your data adds to the existing body of evidence

Your Response was: “Our study with large population data demonstrated different pregnancy

outcomes of immigrant women. Increased risk of GDM, CS and placenta previa were

showed after adjusting maternal age, parity and CCI. This result will help clinicians to

consider different pregnancy outcomes when they meet immigrant women. Eventually,

predicting and preparing for adverse pregnancy outcome in advance will contribute to

improving pregnancy outcomes.”

That information was not included in the discussion section. Besides, there was not an increased risk of placenta previa (the confidence interval starts in1)

I think you should do emphasis on the results presented in table 3.: After adjusting by age, parity and CCI, which are the variables you are expected to adjust by, (considering there were differences between the 2 groups in table 1). Findings are that: to be immigrant increase the risk of having GDM, and CS. But protects against having preeclampsia, and induction.

Reviewer #2: Earlier concerns addressed, paper appears consistent with sections observed with minor changes. I believe the paper is publish-ready

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Adebe Gabriel Aondofa (Ph.D, MPH)

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachment

Submitted filename: koren and inmigrants_2nd.docx

Click here for additional data file. (13.8KB, docx)
PLoS One. 2022 Nov 29;17(11):e0278193. doi: 10.1371/journal.pone.0278193.r004

Author response to Decision Letter 1

25 Apr 2022

Reviewer #1: The paper needs language editing. Consider a language revision.

: We finished language editing as suggested.

When explaining The Charlson Comorbidity Index it would be useful to explain if the higher the score the more comorbid conditions are present (line 110)

: We added this statement in line 112 “that the higher the score the more comorbid conditions are present’

From line 135 to 140 you described table 1, but in the middle of the paragraph there is information related to table 2 (The cesarean section (CS) rate was lower in foreign women than Korean women. The incidence of placental abruption, placental previa, PPH, PH, and UAE

were lower in immigrant women than Korean women.) that information was repeated in line 150.

:We deleted this sentence in line 130.

Table 2. you included: Values are expressed as mean (SD) or %. But there are not values expressed as mean and SD

: We wrote “values are expressed as number, %.”

Table 3. should be named: Odds ratio and 95% confidence intervals of adverse pregnancy out 155 comes of immigrant women instead of Odds ratio and 95% confidence intervals of the risk of adverse pregnancy out 155 comes of immigrant women

: We corrected as suggested.

This sentence is confusing:

In particular, migrant women do not know their past history in their previous country

Which is their past history they don’t know?

: We corrected this sentence as follows; In particular it was difficult to obtain previous medical histories of migrant women in their previous country.

In table 1 it says “Primparity” check spelling

: We corrected as suggested

Line 187: it says risks, it should say odds 190.

: We corrected as suggested

I still see the sentences: In line with this, we previously reported that the birthweight was lower for the children of foreign women than for those of Korean women.[11]

: We deleted this sentence as suggested.

In this sense: I asked you before, Try to stress what your data adds to the existing body of evidence

Your Response was: “Our study with large population data demonstrated different pregnancy

outcomes of immigrant women. Increased risk of GDM, CS and placenta previa were

showed after adjusting maternal age, parity and CCI. This result will help clinicians to

consider different pregnancy outcomes when they meet immigrant women. Eventually,

predicting and preparing for adverse pregnancy outcome in advance will contribute to

improving pregnancy outcomes.”

That information was not included in the discussion section. Besides, there was not an increased risk of placenta previa (the confidence interval starts in1)

: We added this sentences in discussion section. The risk of placenta previa was corrected in abstract, results and discussion.

I think you should do emphasis on the results presented in table 3.: After adjusting by age, parity and CCI, which are the variables you are expected to adjust by, (considering there were differences between the 2 groups in table 1). Findings are that: to be immigrant increase the risk of having GDM, and CS. But protects against having preeclampsia, and induction.

: We added following statement in the first paragraph of discussion (Line 166-168)

Immigrant women were protected against having preeclampsia and PPH and higher risk of GDM and CS compared to Korean women after adjustment for age, parity and CCI.

Attachment

Submitted filename: Response to reviewers after 2nd.docx

Click here for additional data file. (15.9KB, docx)

Decision Letter 2

Rubeena Zakar

10 Jul 2022

PONE-D-21-06981R2Pregnancy outcomes of immigrant women living in Korea: A population-based studyPLOS ONE

Dear Dr.  Ju Jeong,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by 24 August 2022 . If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Rubeena Zakar, Ph.D

Section Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #3: (No Response)

Reviewer #4: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: No

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #3: No

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: All my comments were addressed.

Well done.

I have no further comments.

...........................................................

Reviewer #3: The authors have done well in providing evidence on pregnancy outcomes among immigrants in Korea. Authors could consider the following issues to strengthen the paper.

Introduction

Authors provide a very brief introduction to the topic of interest and seem to miss out important detail. First, about half of the first paragraph focuses on preterm birth and low birth weight and their predictors when the study itself (including analysis) rarely considers these outcomes. Second, the detail on interracial marriage in Korea is great to provide information on the immigration status in Korea. However, the argument is too one-sided and does not feed into the issues raised in the subsequent sentences. I think a reviewer in the earlier revisions of this work raised this issue. Authors could strengthen their introduction by considering the following:

1. What pregnancy outcomes are highly prevalent in Korea?

2. Are there studies that report on these outcomes by immigration status in Korea? Kindly report on this in addition to what has been done in other countries.

3. Justify why immigrants in Korea should be focused.

Methods

1. Authors should provide justification for the duration 2007 - 2016.

2. Can authors clearly define their outcome variables? For instance a number of variables are mentioned and this includes parity and multiple pregnancies which i presume are not the main outcome variables of interest they seek to look at.

3. Regarding section titled "covariates", authors seem to focus mainly on ICC and how it is created from pre-pregnancy factors but there is no information on the specific factors that were combined to create this index. Neither is there information on how this index is created. Is this something that exist in the database or it is an index authors created themselves. Authors should kindly provide more detail regarding this.

4. Since the data for the study covers the period between 2007 and 2016, there is the possibility of multiple pregnancies per woman. How do authors account for this?

5. Line 118: can authors specify the exact group they are referring to?

6. Authors also do not mention the final sample size they used.

7. I think authors should dedicate a section for ethical consideration to outline all forms of ethics that apply to their work; data availability and how it was accessed.

Results

1. lines 131-133: results is not in Table 1. Authors should check this and interpret the other variables in table one in place of this.

Discussion

I find the results to be well discussed and the limitations well laid out.

Reviewer #4: I appreciate the opportunity to review your manuscript. Please find below some important areas in which the manuscript can be clarified or improved from the statistical perspective.

1) The methods section of the manuscript can be better organized by using sub headings e.g. study design and data source, study outcomes, other measures, etc. Please follow the CONSORT guidelines or any other required by the journal.

2) Primary and secondary outcomes must be clearly identified and distinguished in the abstract, methods section, statistical methods, results, and discussion.

3) Please mention all the covariates that were examined in the covariates section of the manuscript.

4) In the statistical analysis section, please include that model was run stepwise and reason behind running 3 separate models.

5) In all the tables in which statistical tests were conducted, the footnotes need to specify which test was used to derive each reported P-value.

6) For age please clarify in the tables if it is mean age or median.

7) Authors have multiple outcome variables but use 0.05 as significance criterion throughout. Please use Bonferroni correction or other method to adjust for multiple testing. Otherwise, the results will have an elevated chance of being false positives.

8) Was there any missing data in your study? How was it handled?

**********

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Reviewer #3: No

Reviewer #4: No

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PLoS One. 2022 Nov 29;17(11):e0278193. doi: 10.1371/journal.pone.0278193.r006

Author response to Decision Letter 2

8 Sep 2022

Response to reviewers

Reviewer #3: The authors have done well in providing evidence on pregnancy outcomes among immigrants in Korea. Authors could consider the following issues to strengthen the paper.

Introduction

Authors provide a very brief introduction to the topic of interest and seem to miss out important detail. First, about half of the first paragraph focuses on preterm birth and low birth weight and their predictors when the study itself (including analysis) rarely considers these outcomes. Second, the detail on interracial marriage in Korea is great to provide information on the immigration status in Korea. However, the argument is too one-sided and does not feed into the issues raised in the subsequent sentences. I think a reviewer in the earlier revisions of this work raised this issue. Authors could strengthen their introduction by considering the following:

1. What pregnancy outcomes are highly prevalent in Korea?

� In South Korea, the incidence of GDM, hypertensive disorder in pregnancy, and preterm birth and the rate of cesarean section have been steadily increasing. GDM accounts for 15.8% in 2017 to 18.01% in 2021, preeclampsia has doubled 2.75% in 2017 to 5.34% in 2021, preterm birth rate was 5.8% in 2010 and 8.5% in 2020

2. Are there studies that report on these outcomes by immigration status in Korea? Kindly report on this in addition to what has been done in other countries.

3. Justify why immigrants in Korea should be focused.

� We appreciate above suggestions mainly focusing on why we need to study immigrant pregnant women and their association with adverse pregnancy outcomes. Therefore we rewrote and organized introduction.

Methods

1. Authors should pro vide justification for the duration 2007 - 2016.

� At the time of planning the study, period between 2007 and 2016 could be accessed and analyzed. In the future, it is also necessary to use this data to see long-term changes.

2. Can authors clearly define their outcome variables? For instance a number of variables are mentioned and this includes parity and multiple pregnancies which i presume are not the main outcome variables of interest they seek to look at.

� We defined variables we looked at as suggested in methods

� Parity and the rate of cesarean section, induction, vacuum delivery, uterine arterial embolization (UAE), and peripartum hysterectomy (PH) were also identified using the presence of a Korea Medical Insurance electronic data interchange (EDI) code.

3. Regarding section titled "covariates", authors seem to focus mainly on ICC and how it is created from pre-pregnancy factors but there is no information on the specific factors that were combined to create this index. Neither is there information on how this index is created. Is this something that exist in the database or it is an index authors created themselves. Authors should kindly provide more detail regarding this.

� CCI was used in this manuscript to represent comorbid status of patients before pregnancy as a simple and widely used method to identify underlying diseases. We added more detail and reference on CCI in the methods.

�The CCI has been known to be a useful and most widely used tool to measure comorbid disease status including cardiovascular diseases, diabetes, malignancies and autoimmune diseases or casemix in health care databases that the higher the score the more comorbid conditions are present. Acute myocardial infarction, Congestive heart failure, Peripheral vascular disease, Cerebral vascular accident, Dementia, Pulmonary disease, Connective tissue disorder, Peptic ulcer, Liver disease, Diabetes, Diabetes complications, Paraplegia, Renal disease, Cancer, Metastatic cancer, Severe liver disease, HIV were analyzed in this study.

4. Since the data for the study covers the period between 2007 and 2016, there is the possibility of multiple pregnancies per woman. How do authors account for this?

� Multiple pregnancies were included in this data set but we did not put as a variable. We also deleted “multiple pregnancy” in method section.

5. Line 118: can authors specify the exact group they are referring to?

� We added following sentence to define group

� (Line 130-131) The Student’s t-test was used to compare continuous variables between Korean and immigrant pregnant women

6. Authors also do not mention the final sample size they used.

� Final sample size was 4,439,778.

7. I think authors should dedicate a section for ethical consideration to outline all forms of ethics that apply to their work; data availability and how it was accessed.

� We added following statement in method.

� Ethical consideration

This study was approved by the Institutional Review Committees of Korea University Guro Hospital (KUGH17273). The informed consent was waived by this IRB because the HIRA database does not include individual identities and because of retrospective nature of this study. This study comprises of third-party data therefore authors cannot share data nor legally distribute.

Results

1. lines 131-133: results is not in Table 1. Authors should check this and interpret the other variables in table one in place of this.

� We corrected result of table 1 in manuscript.

� Table 1 shows the basic characteristics of the study population according to maternal ethnicity. Foreign women were younger and more primiparous than Korean women and tended to have lower CCI score than Korean women.

Discussion

I find the results to be well discussed and the limitations well laid out.

�We appreciate this comment.

Reviewer #4: I appreciate the opportunity to review your manuscript. Please find below some important areas in which the manuscript can be clarified or improved from the statistical perspective.

1) The methods section of the manuscript can be better organized by using sub headings e.g. study design and data source, study outcomes, other measures, etc. Please follow the CONSORT guidelines or any other required by the journal.

� We used following headings in methods.

Study desing-data characteristics-Ethical consideration-Dataset and outcomes-Covariates-Statistical analysis

2) Primary and secondary outcomes must be clearly identified and distinguished in the abstract, methods section, statistical methods, results, and discussion.

� We used ‘main outcome’ and added following sentence in the abstract, method, results and discussion.

� Main outcome of this study were adverse pregnancy outcomes including GDM, preeclampsia, cesarean section, induction of labor, vacuum delivery, placenta previa, placenta abruption, PPH, peripartum hysterectomy and UAE. Age, parity and CCI were adjusted for multiple logistic regression analysis.

3) Please mention all the covariates that were examined in the covariates section of the manuscript.

� CCI used in this study included following diseases.

� Acute myocardial infarction, Congestive heart failure, Peripheral vascular disease, Cerebral vascular accident, Dementia, Pulmonary disease, Connective tissue disorder, Peptic ulcer, Liver disease, Diabetes, Diabetes complications, Paraplegia, Renal disease, Cancer, Metastatic cancer, Severe liver disease, HIV were analyzed in this study.

4) In the statistical analysis section, please include that model was run stepwise and reason behind running 3 separate models.

�We added ‘the model was run stepwise’ in method. The running 3 separate models was conducted to identify the variables that affect the most.

5) In all the tables in which statistical tests were conducted, the footnotes need to specify which test was used to derive each reported P-value.

� We added all the statistical tests used in the footnotes of each tables.

6) For age please clarify in the tables if it is mean age or median.

� For age, the results indicate mean±standard deviation.

7) Authors have multiple outcome variables but use 0.05 as significance criterion throughout. Please use Bonferroni correction or other method to adjust for multiple testing. Otherwise, the results will have an elevated chance of being false positives.

� We appreciate thorough statistical suggestions. In this study, multiple outcome variables were analyzed. Although each variable may be related to each other, each variable is an important subject identified in obstetrics. Therefore, age, parity, and CCI were adjusted in regression model.

8) Was there any missing data in your study? How was it handled?

�This study is based on the claim data and since the diagnosis was confirmed using the icd-10 code, there is no missing data among the mothers charged for delivery. We added this issue in limitation of discussion.

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file. (23.1KB, docx)

Decision Letter 3

Rubeena Zakar

14 Nov 2022

Pregnancy outcomes of immigrant women living in Korea: A population-based study

PONE-D-21-06981R3

Dear Dr. Jeong,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Rubeena Zakar, Ph.D

Section Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #5: All comments have been addressed

Reviewer #6: (No Response)

Reviewer #7: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: In the introduction section from line 88 to line 90 there are empty lines.

Line 147 is should be resultS

Table 2. should be named: “pregnancy outcomes of the study population” without “The”

Table 3. should be named: Odds ratio and 95% confidence intervals of adverse pregnancy outcomes of immigrant women. Check out please you included an extra “155”. It was a cut & paste mistake for sure.

Line 198. Table 3 does not “represents”, I guess you wanted to say “presents”

Also in line 198, I would add the word “unadjusted” in this sentence: “The odds of GDM, preeclampsia, CS, placental abruption, placental previa, PPH, PH, and UAE was lower in foreign women than Korean women.”

In line 215 and 216 why you did not mention the protection against induction?

“Immigrant women were protected against having preeclampsia and PPH and

216 higher risk of GDM, and CS compared to Korean women after adjustment for age, parity, and CCI.”

Line 261 it should be outcomeS

There are still some spelling mistakes. I suggest you perform a language edition to your manuscript.

Reviewer #5: None-------------------------------------------------------------------------------------------------------------------------------------------

Reviewer #6: Appreciate the work of author. Author has clearly mentioned the study population, just a simple question to author about the rational behind selection of 9 years study duration? Is it just because the medical record about pregnancy during that time were available or there is any rational for interracial marriage and pregnancies during that period?

Thank you

Reviewer #7: The title of the study, aim and basic statistical analysis demonstrating pregnancy outcomes between Korean women and immigrant women appear appropriate and linked adequately.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #5: No

Reviewer #6: No

Reviewer #7: Yes: Nnodimele Onuigbo ATULOMAH PhD

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Attachment

Submitted filename: Third review_immigrant Preg outcomes.docx

Click here for additional data file. (12.8KB, docx)

Acceptance letter

Rubeena Zakar

17 Nov 2022

PONE-D-21-06981R3

Pregnancy outcomes of immigrant women living in Korea: A population-based study

Dear Dr. Jeong:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Rubeena Zakar

Section Editor

PLOS ONE

Associated Data

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    Supplementary Materials

    Attachment

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    Submitted filename: koren and inmigrants_2nd.docx

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    Attachment

    Submitted filename: Third review_immigrant Preg outcomes.docx

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    Data Availability Statement

    The access to raw data of the Korean Health Insurance Review and Assessment (HIRA) service is regulated by the Rules for Data Exploration and Utilization of the HIRA. Data are available from the Health Insurance Review and Assessment Service database for researchers who meet the criteria for access to confidential data only after receiving an approval for the data use from the data access committee of the HIRA. HIRA data can be requested through its website (http://opendata.hira.or.kr).

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