Abstract
Objective:
Despite heterogeneity among Pacific Islanders, most studies aggregate them regardless of origin. Thus, limited information is available about perinatal outcomes among various subgroups of Pacific Islanders in the United States, including immigrants from the Republic of the Marshall Islands. We sought to evaluate perinatal outcomes among Marshallese women.
Methods:
We conducted a cross-sectional study of women with at least one singleton live birth between 1997 and 2013 in two Arkansas counties using birth certificate data from the Arkansas Department of Health. Unadjusted and adjusted prevalence ratios (PR) and 95% confidence intervals (CI) were calculated from modified Poisson regression models.
Results:
Of the 91,662 singleton births in both counties during the study period, 2,488 were to Marshallese women. In adjusted analyses, Marshallese women had higher prevalence of “other medical risk factors” (PR=1.47; 95% CI: 1.30, 1.65) than NH white women. Marshallese women had higher rates of precipitous labor and fetal distress during labor compared to NH white women (PR=2.65; 95% CI: 2.22, 3.17 and 1.89; 95% CI: 1.62, 2.21, respectively). Marshallese were also more likely to have tocolysis (PR=1.43; 95% CI: 1.16, 1.76), forceps (PR=1.68; 95% CI: 1.16, 2.43) or vacuum (PR=1.89; 95% CI: 1.60, 2.22) used in delivery and cesarean section (PR=1.13; 95% CI: 1.01, 1.27). Marshallese infants had a higher rates of anemia (PR=3.10; 95% CI: 2.01, 4.77), birth injury (PR=2.13; 95% CI: 1.50, 3.03), assisted ventilation <30 minutes (PR=2.11; 95% CI: 1.64, 2.71), preterm birth (PR=1.67; 95% CI: 1.50, 1.83), and small-for-gestational age (PR=1.25; 95% CI: 1.12–1.39) than NH white infants.
Conclusions:
Marshallese women and infants had higher rates of adverse perinatal outcomes compared to their NH white counterparts. Additional studies are needed to determine if perinatal outcomes among the Marshallese differed from other Pacific Islander subgroups.
Keywords: Infant, low birth weight, Marshall Islands, Marshallese, Pacific Islander, pregnancy, preterm birth
INTRODUCTION
Pacific Islanders are one of the fastest growing populations in the United States (US), growing three times faster between 2000 and 2010 than the total US population.(Hixson, 2012) The most rapid growth is occurring in the Southern US (66% increase), particularly in the state of Arkansas (252% increase).(Hixson, 2012) The vast majority of Pacific Islanders in Arkansas are immigrants from the Republic of the Marshall Islands (RMI).(Central Intelligence Agency. World Factbook:Marshall Islands, 2014)Arkansas has the largest population of Marshallese in the continental US.(Hixson, 2012) Between 1947 and 1986, the RMI were administratively controlled by the US as a United Nations Trust Territory of the Pacific Islands.(McElfish, Hallgren, & Yamada, 2015) The RMI became an independent country in 1986 under the Compact of Free Association (COFA). The COFA allows people in these territories to freely enter, lawfully reside, and work in the US without visas; thus, the precise number of COFA immigrants is difficult to ascertain.(McElfish et al., 2015) Based on US Census estimates, migration from the RMI to Arkansas and other US states tripled between 2000 and 2010 from 6,700 to 22,434. However, the true number of Marshallese living in the US is estimated to be much higher. Based on school enrollment data, we estimated that about 40,000 COFA migrants live in the US and approximately 10,000 to 12,000 live in Arkansas.(McElfish et al., 2015) With increasing changes in climate and declining employment opportunities in the RMI, the Marshallese population is likely to increase in the US.(Yamada, 2004)
Based on the projected increase in the Marshallese population in the US, obstetric providers throughout the US will encounter increasing numbers of Marshallese women in their practice; however, a paucity of published literature exists on perinatal outcomes among Marshallese immigrants. Most research aggregate data on Pacific Islanders and Asian Americans, which obscures the substantial differences between ethnic subgroups.(The American Community—Pacific Islanders: 2004, 2007; Park, Braun, Horiuchi, Tottori, & Onaka, 2009; Ro & Yee, 2010; Roehr, 2010; Srinivasan & Guillermo, 2000; Working Group of the Applied Research Center, 2013) As a result, most information available about perinatal outcomes are reported for “Asians/Pacific Islanders” or for all Pacific Islanders in aggregate. The few studies that report perinatal outcomes for subgroups among Pacific Islanders report outcomes for Hawaiians, Samoans, Guamanian and Micronesian populations and show heterogeneity in perinatal outcomes between the subgroups;(Chang, Hurwitz, Miyamura, Kaneshiro, & Sentell, 2015; Rao, Daniels, El-Sayed, Moshesh, & Caughey, 2006; Schempf, Mendola, Hamilton, Hayes, & Makuc, 2010; Tsitas, Schmid, Oehler, & Tempfer, 2015; Wong et al., 2008) thus extrapolating findings from these populations to Marshallese women may not be appropriate. Therefore, the intent of this investigation was to compare obstetric and newborn outcomes between immigrant Marshallese women and non-Hispanic (NH) white, NH black, and Hispanic women.
METHODS
A cross-sectional study was conducted using vital records data from the Arkansas Department of Health, Health Statistics Branch. The Institutional Review Board (IRB) approval was obtained prior to the study being conducted. The study population consisted of all resident women from two counties in Arkansas (Benton and Washington), who had one or more singleton, live births between January 1, 1997, and December 31, 2013. Benton and Washington counties were selected because more than 95% of the Marshallese population in Arkansas resides in these counties.
Maternal information obtained from birth records included maternal age (<20, 20–29, 30–39, ≥40 years); education ((elementary (1–8 years of schooling), secondary (9–12 years), some college or higher (≥13 years)); marital status (married/unmarried); parity (1, 2, or ≥3 children); prenatal care; medical risk factors; obstetric procedures; complications of labor; and method of delivery. Maternal ethnicity (NH white, NH black, Hispanic, and Marshallese) was also obtained from birth records. Women were categorized as Marshallese if the birth certificate indicated that the mother was born in the Marshall Islands. Women who were not NH white, NH black, Hispanic or Marshallese were excluded from the study.
Infant information obtained from birth certificate records included sex, birthweight (<1500, 1500–2499, 2500–4000, and >4000 grams), gestational age (<20, 20–36, ≥37 completed weeks of gestation), and abnormal conditions of newborns. Infant weight was further categorized as small-for-gestational-age (SGA; birthweights <10th percentile), appropriate-for-gestational-age (AGA; birthweights from 10th to 90th percentiles), and large-for-gestational-age (LGA; birthweights >90th percentile) based on gestational age using nationally representative growth curves.(Alexander, Tompkins, Allen, & Hulsey, 1999)
Statistical analyses
Summary statistics were computed for all study variables and expressed as means (standard deviation) for continuous variables and counts (percentage) for categorical variables. Chi-square and ANOVA tests were used for the comparison across racial groups (Tables 1 and 2). Prevalence-at-livebirth for selected birth defects was calculated as per 10,000 live births. Crude prevalence ratios (PR) and 95% confidence intervals (CI) were also calculated using NH white women as the reference group. Adjusted PRs and 95% CIs were calculated adjusting for maternal age, education, marital status, and parity in multivariable modified Poisson regression analyses. Statistical significance was set at P<0.05 or if the confidence interval excluded the null value. All statistical analyses were performed using SAS 9.1 software (SAS Inc., Cary, NC).
Table 1.
Number and Percentages for Sociodemographic Characteristics of Marshallese Mothers, Benton and Washington Counties, Arkansas, 1997–2013 (n=91,622)
| NH White (n=65,800) | NH Black (n=1,680) | Hispanic (n=21,654) | Marshallese (n=2,488) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| n | % | n | % | n | % | n | % | p | |
| Maternal age | <0.01 | ||||||||
| <20 years | 7081 | 10.8 | 220 | 13.1 | 2,946 | 13.6 | 220 | 8.9 | |
| 20–29 years | 38,335 | 58.3 | 981 | 58.4 | 12,209 | 56.4 | 1,675 | 67.4 | |
| 30–39 years | 19,368 | 29.4 | 454 | 27.0 | 6,032 | 27.9 | 581 | 23.4 | |
| ≥40 years | 1,000 | 1.5 | 25 | 1.5 | 461 | 2.1 | 11 | 0.4 | |
| Maternal Education | <0.01 | ||||||||
| Elementary (1–8 years) | 697 | 1.1 | 6 | 0.4 | 6,591 | 31.5 | 149 | 6.5 | |
| Secondary (9–12 years) | 31,111 | 47.6 | 672 | 40.8 | 11,763 | 56.2 | 1,978 | 85.7 | |
| Some college or higher (≥13 years) | 33,594 | 51.4 | 969 | 58.8 | 2,572 | 12.3 | 180 | 7.8 | |
| Marital Status | <0.01 | ||||||||
| Married | 48,689 | 74.0 | 788 | 46.9 | 12,517 | 57.8 | 781 | 31.4 | |
| Unmarried | 17,068 | 26.0 | 892 | 53.1 | 9,133 | 42.2 | 1,706 | 68.6 | |
| Parity | <0.01 | ||||||||
| 1 child | 28,524 | 43.4 | 745 | 44.4 | 7,215 | 33.4 | 562 | 22.7 | |
| 2 children | 20,161 | 30.7 | 467 | 27.9 | 6,007 | 27.8 | 503 | 20.3 | |
| ≥3 children | 16,997 | 25.9 | 465 | 27.7 | 8,382 | 38.8 | 1,414 | 57.0 | |
| Prenatal care | |||||||||
| Prenatal care in the 1st trimester | 58,522 | 87.4 | 1,433 | 83.4 | 15,835 | 73.2 | 1,262 | 52.2 | <0.01 |
| No prenatal care | 840 | 1.3 | 57 | 3.4 | 524 | 2.4 | 480 | 19.3 | <0.01 |
NH=Non-Hispanic; SD=Standard deviation.
Table 2.
Means and Standard Deviations for Sociodemographic Characteristics of Marshallese Mothers, Benton and Washington Counties, Arkansas, 1997–2013 (n=91,622)
| NH White (n=65,800) | NH Black (n=1,680) | Hispanic (n=21,654) | Marshallese (n=2,488) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | p | |
| Maternal age | 26.6 | 5.7 | 26.2 | 5.8 | 26.4 | 6.1 | 25.8 | 5.2 | <0.01 |
| Maternal education | 13.5 | 2.3 | 13.8 | 2.3 | 9.8 | 3.3 | 11.3 | 1.5 | <0.01 |
| Parity | 2.0 | 1.2 | 2.1 | 1.3 | 2.4 | 1.4 | 3.1 | 1.9 | <0.01 |
NH=Non-Hispanic; SD=Standard deviation.
The research was conducted in accordance with the prevailing ethical principles and was deemed exempt by the Institutional Review Board at the University of Arkansas for Medical Sciences. The research was approved by the Arkansas Department of Health, Science Advisory Committee.
RESULTS
During the study period, 649,957 infants were born to resident women in Arkansas (68.5% non-Hispanic white, 19.7% non-Hispanic black, 9.1% Hispanic), of which 2,567 (0.4%) were to immigrant Marshallese women. Of those births, 99,045 (15.3%) occurred to resident women in Benton and Washington Counties. Of the 99,045 births, 7,423 live births were excluded because they did not meet the study criteria (2,741 were not singletons, and maternal ethnicity of 4,682 births did not fit the study categories or were missing), leaving a total of 91,622 singleton infants in our study (Table 1). In both counties combined, 2,488 (2.6%) singleton births were to Marshallese women. As seen in Tables 1 and 2, Marshallese women tended to have only 9–12 years of education, be unmarried, and have three or more children. Only 52% of Marshallese women received prenatal care in the first trimester, whereas 73% of Hispanic women and more than 80% of NH black and NH white women received prenatal care in the first trimester. Fifteen percent of Marshallese women received no prenatal care.
Maternal outcomes
Medical Risk Factors and Obstetric Outcomes
Prevalence rates of medical risk factors and obstetric outcomes by maternal ethnicity are presented in Table 3. About 80% of pregnant women (78% Marshallese, 78.3% NH black, 81% NH white, and 82.8% Hispanic) had no known medical risk factors for an adverse pregnancy outcome. The frequency of alcohol and tobacco use during pregnancy was relatively low among Marshallese women (0.3% and 2.3%). The highest rates of alcohol use during pregnancy were among NH black and NH white women (0.8% and 0.7%, respectively). NH white women had the highest rates of prenatal tobacco use (13.9%) followed by NH black women (8.0%). Although only 52% of Marshallese women received prenatal care in the first trimester of pregnancy, 74% had an ultrasound during pregnancy which was the highest of all racial/ethnic groups (70.2% for NH blacks, 65.1% for NH whites and 58.9% for Hispanics). Similarly, electronic fetal monitoring was used more often in Marshallese.
Table 3.
Prevalence of Medical Risk Factors and Obstetric Procedures by Maternal Ethnicity, Benton and Washington Counties, Arkansas, 1997–2013
| NH White | NH Black | Hispanic | Marshallese | ||||||
|---|---|---|---|---|---|---|---|---|---|
| (n=65,800) | (n=1,680) | (n=21,654 ) | (n=2,488) ) | p | |||||
| n | % | n | % | n | % | n | % | ||
| MEDICAL RISK FACTORS | |||||||||
| No medical risk factors | 53,303 | 81.0 | 1,316 | 78.3 | 17,958 | 82.9 | 1,940 | 78.0 | <0.01 |
| Anemia (Hct.<30/Hgb <10) | 969 | 1.5 | 52 | 3.1 | 266 | 1.2 | 48 | 1.9 | <0.01 |
| Cardiac disease | 259 | 0.4 | 6 | 0.4 | 32 | 0.2 | 6 | 0.2 | <0.01 |
| Acute or chronic lung disease | 794 | 1.2 | 18 | 1.1 | 108 | 0.5 | 3 | 0.1 | <0.01 |
| Diabetes | 1,561 | 2.4 | 51 | 3.0 | 1,006 | 4.7 | 81 | 3.3 | <0.01 |
| Genital herpes | 765 | 1.2 | 37 | 2.2 | 86 | 0.4 | 8 | 0.3 | <0.01 |
| Polyhydramnios/oligohydramnios | 527 | 0.8 | 14 | 0.8 | 279 | 1.3 | 35 | 1.4 | <0.01 |
| Hemoglobinopathy | 6 | 0.0 | 2 | 0.1 | 1 | 0.0 | 0 | 0.0 | <0.01 |
| Hypertension, chronic | 527 | 0.8 | 28 | 1.7 | 91 | 0.4 | 9 | 0.4 | <0.01 |
| Hypertension, pregnancy associated | 2,435 | 3.7 | 54 | 3.2 | 575 | 2.7 | 26 | 1.1 | <0.01 |
| Eclampsia | 101 | 0.2 | 2 | 0.1 | 34 | 0.2 | 0 | 0 | 0.25 |
| Incompetent cervix | 82 | 0.1 | 6 | 0.4 | 30 | 0.1 | 0 | 0 | <0.05 |
| Previous infant ≥4000 grams | 837 | 1.3 | 14 | 0.8 | 255 | 1.2 | 25 | 1.0 | 0.20 |
| Previous preterm or small infant | 975 | 1.5 | 32 | 1.9 | 323 | 1.5 | 58 | 2.3 | <0.01 |
| Renal disease | 129 | 0.2 | 2 | 0.1 | 22 | 0.1 | 8 | 0.3 | <0.05 |
| Rh sensitization | 220 | 0.3 | 2 | 0.1 | 23 | 0.1 | 0 | 0 | <0.01 |
| Uterine bleeding | 356 | 0.5 | 6 | 0.4 | 94 | 0.4 | 5 | 0.2 | <0.05 |
| Other medical risk factors | 4,513 | 6.9 | 163 | 9.7 | 1,153 | 5.3 | 320 | 12.9 | <0.01 |
| Alcohol use during pregnancy | 442 | 0.7 | 13 | 0.8 | 61 | 0.3 | 8 | 0.3 | <0.01 |
| Tobacco use during pregnancy | 9,147 | 13.9 | 135 | 8.0 | 293 | 1.4 | 58 | 2.3 | <0.01 |
| OBSTETRIC PROCEDURES | |||||||||
| No obstetric procedure | 2,633 | 4.0 | 76 | 4.5 | 687 | 3.2 | 67 | 2.7 | <0.01 |
| Amniocentesis | 1,008 | 1.5 | 24 | 1.4 | 153 | 0.7 | 12 | 0.5 | <0.01 |
| Electronic fetal monitoring | 50,176 | 76.3 | 1,260 | 75.0 | 17,822 | 82.3 | 2,143 | 86.1 | <0.01 |
| Induction of labor | 15,476 | 23.5 | 260 | 15.5 | 3,582 | 16.5 | 108 | 4.3 | <0.01 |
| Stimulation of labor | 9,249 | 14.1 | 196 | 11.7 | 3,501 | 16.2 | 342 | 13.8 | <0.01 |
| Tocolysis | 1,487 | 2.3 | 41 | 2.4 | 576 | 2.7 | 101 | 4.1 | <0.01 |
| Ultrasound | 42,835 | 65.1 | 1,179 | 70.2 | 12,763 | 58.9 | 1,836 | 73.8 | <0.01 |
| Other obstetric procedures | 2,631 | 4.0 | 79 | 4.7 | 777 | 3.6 | 91 | 3.7 | <0.05 |
| COMPLICATIONS OF LABOR | |||||||||
| No complications of labor or delivery | 47,002 | 71.4 | 1,161 | 69.1 | 15,334 | 70.8 | 1,493 | 60.0 | <0.01 |
| Febrile (>100°F or 38°C) | 784 | 1.2 | 14 | 0.8 | 339 | 1.6 | 18 | 0.7 | <0.01 |
| Meconium, moderate/heavy | 2,059 | 3.1 | 52 | 3.1 | 1,012 | 4.7 | 104 | 4.2 | <0.01 |
| Premature rupture of membrane >12hrs | 989 | 1.5 | 15 | 0.9 | 306 | 1.4 | 25 | 1.0 | <0.05 |
| Abruptio placenta | 280 | 0.4 | 8 | 0.5 | 77 | 0.4 | 12 | 0.5 | 0.49 |
| Placenta previa | 160 | 0.2 | 2 | 0.1 | 59 | 0.3 | 5 | 0.2 | 0.59 |
| Other excessive bleeding | 191 | 0.3 | 2 | 0.1 | 102 | 0.5 | 7 | 0.3 | <0.01 |
| Seizures during labor | 16 | 0 | 4 | 0.2 | 10 | 0.1 | 1 | 0 | <0.01 |
| Precipitate labor | 1,138 | 1.7 | 29 | 1.7 | 723 | 3.3 | 175 | 7.0 | <0.01 |
| Prolonged labor (>20 hours) | 337 | 0.5 | 5 | 0.3 | 82 | 0.4 | 3 | 0.1 | <0.01 |
| Dysfunctional labor | 2,107 | 3.2 | 48 | 2.9 | 600 | 2.8 | 42 | 1.7 | <0.01 |
| Breech/malpresentation | 2,283 | 3.5 | 42 | 2.5 | 743 | 3.4 | 101 | 4.1 | 0.06 |
| Cephalopelvic disproportion | 961 | 1.5 | 18 | 1.1 | 313 | 1.5 | 7 | 0.3 | <0.01 |
| Cord prolapse | 141 | 0.2 | 1 | 0.1 | 35 | 0.2 | 6 | 0.2 | 0.24 |
| Anesthetic complications | 41 | 0.1 | 0 | 0 | 4 | 0 | 1 | 0 | 0.07 |
| Fetal distress | 3,052 | 4.6 | 90 | 5.4 | 848 | 3.9 | 189 | 7.6 | <0.01 |
| Other complications of labor and delivery | 8,280 | 12.6 | 278 | 17 | 2,517 | 11.6 | 513 | 20.6 | <0.01 |
| METHOD OF DELIVERY | |||||||||
| Vaginal delivery | 49,641 | 75.4 | 1,191 | 71 | 16,299 | 75.3 | 1,852 | 74.4 | <0.01 |
| Vaginal birth after prior C-section | 724 | 1.1 | 13 | 0.8 | 341 | 1.6 | 36 | 1.5 | <0.01 |
| Primary C-section | 8,826 | 13.4 | 271 | 16 | 2,230 | 10.3 | 280 | 11.3 | <0.01 |
| Repeat C-section | 6,557 | 10.0 | 203 | 12 | 2,778 | 12.8 | 319 | 12.8 | <0.01 |
| Forceps | 1,038 | 1.6 | 20 | 1.2 | 185 | 0.9 | 32 | 1.3 | <0.01 |
| Vacuum | 3,204 | 4.9 | 64 | 3.8 | 938 | 4.3 | 155 | 6.2 | <0.01 |
NH=Non-Hispanic
Hct: hematocrit; Hgb: hemoglobin
In multivariable analyses (Table 4), compared to NH-white women, Marshallese women tended toward a higher prevalence of renal disease, but the increase was not statistically significant (PR=1.45; 95% CI: 0.70, 2.98). With the exception of “other medical risk factors,” which were more prevalent in Marshallese compared to NH white (PR=1.47; 95% CI: 1.30, 1.65), the prevalence of all other conditions of all other conditions were similar between the groups. During pregnancy, Marshallese women were more likely to have polyhydramnios or oligohydramnios (PR=1.4, 95% CI: 1.0, 2.0), tocolysis (PR=1.43; 95% CI: 1.16, 1.76), and ultrasound (PR=1.16; 95% CI: 1.13, 1.19) than NH white women.
Table 4.
Prevalence Rates (PR) and 95% Confidence Intervals (CI) for Medical Risk Factors and Obstetric Procedures by Maternal Race/Ethnicity, Benton and Washington Counties, Arkansas, 1997–2013
| NH-Black | Hispanic | Marshallese | ||||
|---|---|---|---|---|---|---|
| (n=1,680) | (n=21,654 ) | (n=2,488 ) | ||||
| PR (95% CI) | PR* (95% CI) | PR (95% CI) | PR* (95% CI) | PR (95% CI) | PR* (95% CI) | |
| MEDICAL RISK FACTORS | ||||||
| No medical risk factors | 0.96 (0.94–0.98) | 0.97 (0.94–0.99) | 1.02 (1.01–1.03) | 1.04 (1.04–1.05) | 0.96 (0.94–0.98) | 1.01 (0.99–1.03) |
| Anemia (Hct <30/Hgb <10) | 1.94 (1.47–2.55) | 1.90 (1.44–2.51) | 0.82 (0.72–0.94) | 0.80 (0.68–0.93) | 1.25 (0.94–1.67) | 0.84 (0.60–1.17) |
| Cardiac disease | 0.88 (0.39–1.97) | 0.91 (0.40–2.06) | 0.40 (0.28–0.57) | 0.49 (0.32–0.74) | 0.82 (0.41–1.66) | 1.01 (0.49–2.09) |
| Acute or chronic lung disease | 1.02 (0.67–1.55) | 0.98 (0.64–1.52) | 0.42 (0.35–0.51) | 0.43 (0.34–0.54) | 0.10 (0.03–0.31) | 0.06 (0.02–0.25) |
| Diabetes | 1.38 (1.07–1.78) | 1.47 (1.13–1.91) | 1.93 (1.79–2.08) | 1.45 (1.30–1.61) | 1.36 (1.09–1.69) | 1.11 (0.88–1.41) |
| Genital herpes | 1.80 (1.30–2.49) | 1.68 (1.20–2.36) | 0.34 (0.27–0.42) | 0.34 (0.26–0.45) | 0.27 (0.13–0.54) | 0.19 (0.08–0.45) |
| Polyhydramnios/oligohydramnios | 0.97 (0.57–1.65) | 1.00 (0.58–1.7) | 1.58 (1.37–1.82) | 1.37 (1.14–1.65) | 1.69 (1.20–2.37) | 1.38 (0.95–2.01) |
| Hemoglobinopathy | 10.96 (2.28–52.72) | 11.59 (2.59–51.97) | 0.44 (0.05–3.58) | 0.37 (0.01–10.06) | - | - |
| Hypertension, chronic | 2.08 (1.44–2.99) | 2.35 (1.63–3.38) | 0.53 (0.43–0.66) | 0.43 (0.32–0.57) | 0.44 (0.23–0.85) | 0.53 (0.27–1.04) |
| Hypertension, pg associated | 0.97 (0.76–1.23) | 1.01 (0.79–1.29) | 0.72 (0.66–0.79) | 0.72 (0.65–0.80) | 0.27 (0.18–0.40) | 0.34 (0.23–0.51) |
| Eclampsia | 1.30 (0.48–3.52) | 1.55 (0.55–4.35) | 0.88 (0.60–1.29) | 0.91 (0.55–1.51) | - | - |
| Incompetent cervix | 2.47 (1.08–5.63) | 2.39 (1.03–5.57) | 0.99 (0.66–1.49) | 1.25 (0.75–2.11) | - | - |
| Previous infant ≥4000 grams | 0.63 (0.37–1.07) | 0.65 (0.39–1.11) | 0.94 (0.82–1.08) | 0.84 (0.71–0.99) | 0.78 (0.53–1.16) | 0.57 (0.37–0.89) |
| Previous preterm or small infant | 1.27 (0.91–1.78) | 1.16 (0.82–1.65) | 1.01 (0.89–1.14) | 0.91 (0.78–1.07) | 1.62 (1.26–2.09) | 0.87 (0.65–1.15) |
| Renal disease | 0.57 (0.14–2.30) | 0.56 (0.14–2.24) | 0.50 (0.32–0.78) | 0.43 (0.26–0.74) | 1.59 (0.78–3.24) | 1.45 (0.70–2.98) |
| Rh sensitization | 0.35 (0.09–1.41) | 0.39 (0.10–1.56) | 0.32 (0.21–0.49) | 0.39 (0.23–0.66) | - | - |
| Uterine bleeding | 0.61 (0.27–1.36) | 0.66 (0.30–1.48) | 0.76 (0.61–0.95) | 0.69 (0.52–0.92) | 0.36 (0.15–0.87) | 0.34 (0.14–0.83) |
| Other medical risk factors | 1.42 (1.23–1.64) | 1.32 (1.13–1.53) | 0.77 (0.72–0.82) | 0.70 (0.65–0.76) | 1.85 (1.67–2.05) | 1.47 (1.30–1.65) |
| Alcohol use during pregnancy | 1.29 (0.77–2.15) | 1.18 (0.71–1.96) | 0.42 (0.32–0.55) | 0.34 (0.24–0.48) | 0.48 (0.24–0.96) | 0.36 (0.18–0.74) |
| Tobacco use during pregnancy | 0.59 (0.50–0.69) | 0.52 (0.44–0.60) | 0.10 (0.09–0.11) | 0.02 (0.02–0.03) | 0.17 (0.13–0.22) | 0.06 (0.05–0.08) |
| OBSTETRIC PROCEDURES | ||||||
| No obstetric procedure performed | 1.14 (0.92–1.42) | 1.19 (0.95–1.49) | 0.79 (0.73–0.86) | 0.64 (0.58–0.71) | 0.69 (0.55–0.87) | 0.60 (0.46–0.77) |
| Amniocentesis | 0.94 (0.64–1.38) | 1.02 (0.70–1.50) | 0.46 (0.39–0.54) | 0.49 (0.40–0.60) | 0.31 (0.18–0.55) | 0.51 (0.28–0.90) |
| Electronic fetal monitoring | 0.99 (0.96–1.02) | 0.97 (0.94–0.99) | 1.08 (1.07–1.09) | 1.11 (1.10–1.12) | 1.13 (1.11–1.15) | 1.09 (1.07–1.11) |
| Induction of labor | 0.65 (0.58–0.73) | 0.67 (0.59–0.74) | 0.71 (0.69–0.73) | 0.77 (0.74–0.80) | 0.19 (0.16–0.23) | 0.20 (0.17–0.25) |
| Stimulation of labor | 0.83 (0.73–0.95) | 0.83 (0.73–0.95) | 1.15 (1.11–1.19) | 1.15 (1.10–1.20) | 0.99 (0.90–1.09) | 1.04 (0.93–1.15) |
| Tocolysis | 1.46 (1.14–1.87) | 1.43 (1.11–1.84) | 1.13 (1.03–1.24) | 1.08 (0.96–1.21) | 1.70 (1.40–2.06) | 1.43 (1.16–1.76) |
| Ultrasound | 1.08 (1.05–1.11) | 1.09 (1.06–1.12) | 0.90 (0.89–0.91) | 0.88 (0.87–0.89) | 1.13 (1.10–1.16) | 1.16 (1.13–1.19) |
| Other obstetric procedures | 1.30 (1.07–1.58) | 1.31 (1.08–1.6) | 0.89 (0.83–0.96) | 0.90 (0.82–0.99) | 0.89 (0.73–1.09) | 0.90 (0.72–1.12) |
| COMPLICATIONS OF LABOR | ||||||
| No complications of labor/delivery | 0.96 (0.93–0.99) | 0.97 (0.93–1.00) | 0.99 (0.98–1.00) | 0.99 (0.98–1.00) | 0.84 (0.81–0.87) | 0.82 (0.79–0.85) |
| Febrile (>100°F or 38°C) | 0.87 (0.55–1.38) | 0.70 (0.42–1.17) | 1.30 (1.15–1.47) | 1.59 (1.37–1.84) | 0.61 (0.38–0.97) | 0.80 (0.48–1.34) |
| Meconium, moderate/heavy | 0.97 (0.74–1.27) | 0.95 (0.72–1.25) | 1.50 (1.39–1.61) | 1.35 (1.23–1.48) | 1.35 (1.11–1.64) | 1.34 (1.08–1.65) |
| Premature rupture of membrane >12hrs | 1.14 (0.80–1.62) | 1.05 (0.72–1.53) | 0.90 (0.79–1.02) | 0.90 (0.77–1.05) | 0.62 (0.42–0.92) | 0.79 (0.52–1.20) |
| Abruptio placenta | 1.05 (0.52–2.12) | 0.99 (0.49–2.02) | 0.83 (0.65–1.06) | 0.60 (0.43–0.84) | 1.10 (0.62–1.96) | 0.69 (0.38–1.26) |
| Placenta previa | 0.47 (0.12–1.89) | 0.52 (0.13–2.11) | 1.15 (0.86–1.54) | 1.03 (0.69–1.55) | 0.82 (0.34–1.99) | 0.71 (0.27–1.84) |
| Other excessive bleeding | 0.38 (0.09–1.53) | 0.41 (0.10–1.65) | 1.56 (1.23–1.98) | 1.50 (1.12–2.02) | 0.94 (0.44–2.00) | 1.00 (0.45–2.21) |
| Seizures during labor | 9.59 (3.21–28.66) | 9.53 (2.76–32.88) | 1.92 (0.87–4.23) | 2.37 (0.87–6.41) | 1.68 (0.22–12.66) | 1.14 (0.16–7.92) |
| Precipitate labor | 1.12 (0.80–1.57) | 0.95 (0.66–1.37) | 1.93 (1.76–2.11) | 1.51 (1.35–1.69) | 4.17 (3.58–4.85) | 2.65 (2.22–3.17) |
| Prolonged labor (>20 hours) | 0.57 (0.24–1.38) | 0.64 (0.26–1.55) | 0.74 (0.58–0.94) | 0.94 (0.70–1.25) | 0.24 (0.08–0.75) | 0.44 (0.14–1.38) |
| Dysfunctional labor | 0.90 (0.68–1.19) | 0.91 (0.69–1.20) | 0.86 (0.79–0.94) | 0.99 (0.89–1.10) | 0.53 (0.39–0.72) | 0.89 (0.65–1.21) |
| Breech/malpresentation | 0.83 (0.65–1.07) | 0.84 (0.65–1.08) | 0.96 (0.89–1.03) | 0.93 (0.85–1.02) | 1.08 (0.90–1.30) | 1.05 (0.85–1.28) |
| Cephalopelvic disproportion | 0.71 (0.45–1.13) | 0.77 (0.48–1.22) | 1.00 (0.88–1.13) | 1.23 (1.05–1.43) | 0.19 (0.09–0.40) | 0.33 (0.15–0.74) |
| Cord prolapse | 1.05 (0.39–2.83) | 1.10 (0.40–3.04) | 0.74 (0.51–1.07) | 0.53 (0.34–0.82) | 1.10 (0.49–2.49) | 0.98 (0.41–2.36) |
| Anesthetic complications | - | - | 0.43 (0.18–1.01) | 0.54 (0.19–1.54) | 0.63 (0.09–4.57) | 0.70 (0.09–5.41) |
| Fetal distress | 1.12 (0.91–1.37) | 1.13 (0.92–1.39) | 0.84 (0.78–0.90) | 0.82 (0.75–0.90) | 1.62 (1.41–1.87) | 1.89 (1.62–2.21) |
| Other complications of labor and delivery | 1.33 (1.20–1.48) | 1.27 (1.14–1.41) | 0.92 (0.88–0.96) | 1.00 (0.95–1.05) | 1.63 (1.51–1.76) | 1.67 (1.53–1.82) |
| METHOD OF DELIVERY | ||||||
| Vaginal delivery | 0.93 (0.90–0.96) | 0.94 (0.91–0.96) | 1.00 (0.99–1.01) | 0.99 (0.98–1.00) | 1.00 (0.98–1.02) | 1.00 (0.97–1.02) |
| Vaginal birth after prior C-section | 0.69 (0.40–1.19) | 0.64 (0.35–1.17) | 1.45 (1.28–1.65) | 1.32 (1.12–1.55) | 1.33 (0.95–1.85) | 0.93 (0.65–1.34) |
| Primary C-section | 1.24 (1.12–1.37) | 1.22 (1.11–1.35) | 0.77 (0.74–0.80) | 0.88 (0.84–0.92) | 0.80 (0.72–0.89) | 1.13 (1.01–1.27) |
| Repeat C-section | 1.16 (1.02–1.32) | 1.19 (1.04–1.35) | 1.29 (1.24–1.34) | 1.23 (1.17–1.30) | 1.28 (1.15–1.42) | 0.91 (0.81–1.03) |
| Forceps | 0.87 (0.58–1.30) | 0.93 (0.62–1.39) | 0.54 (0.46–0.63) | 0.73 (0.62–0.87) | 0.81 (0.57–1.15) | 1.68 (1.16–2.43) |
| Vacuum | 0.80 (0.63–1.01) | 0.84 (0.66–1.07) | 0.89 (0.83–0.96) | 0.95 (0.87–1.03) | 1.32 (1.13–1.54) | 1.89 (1.60–2.22) |
NH=Non-Hispanic; PR=Prevalence Ratio; Hct: hematocrit; Hgb: hemoglobin
Adjusted by maternal age, education, parity, and marital status
Complications of Labor
The prevalence of complications of labor for each ethnic group are displayed in Table 3. Approximately 30% of NH white, NH black, and Hispanic women experienced complications during labor or delivery; whereas, 40% of Marshallese women experienced complications. Seven percent of Marshallese women had precipitous labor (a labor lasting less than two hours) while only 1.7% of NH white and NH black women and 3.3% of Hispanic had precipitous labor. Eight percent of Marshallese women experienced fetal distress during labor, compared to 5% of NH white and NH black women and 4% of Hispanic women. Twenty-one percent of Marshallese women had “other complications of labor and delivery,” which was more frequent than the other racial/ethnic groups (12.6% for NH white, 17% for NH black, and 11.6% for Hispanic women).
After adjusting for potential confounders, Marshallese women were more likely to have several complications of labor (Table 4). They were more likely to have moderate/heavy meconium in their amniotic fluid (PR=1.34; 95% CI: 1.08, 1.65), precipitous labor (PR=2.65; 95% CI: 2.22, 3.17), fetal distress (PR=1.89; 95% CI: 1.62, 2.21), and other complications of labor or delivery (PR=1.67; 95% CI: 1.53, 1.82).
Method of Delivery
As seen in Table 3, Marshallese women had similar frequency of vaginal delivery and vaginal births after cesarean delivery to the other ethnic groups. After adjusting for potential confounders, Marshallese women were more likely to have a primary cesarean delivery (PR=1.13; 95% CI: 1.01, 1.27), forceps (PR=1.68; 95% CI: 1.16, 2.43), and a vacuum-assisted delivery (PR=1.89; 95% CI: 1.60, 2.22) compared to NH white women.
Infant Outcomes
The prevalence of infant outcomes is displayed in Tables 4 and 5 by maternal ethnicity. Eight percent of Marshallese and NH black infants were born low birthweight (1500–2499 grams); mean birthweights of Marshallese and NH black infants were 3,110 and 3,134 grams, respectively. Only 3.7% of Marshallese infants were born macrosomic (>4000 grams). Nineteen percent of Marshallese infants were born moderately preterm (32–36 weeks). Fifteen percent of Marshallese and 15.9% of NH black infants were born small-for-gestational age. Of the ethnic groups, Marshallese infants had the highest prevalence of anemia, birth injury, meconium aspiration, assisted ventilation less than 30 minutes, and “other abnormal conditions of the infant.”
Table 5.
Prevalence of Infant Outcomes by Maternal Race/Ethnicity, Benton and Washington Counties, Arkansas, 1997–2013
| NH White | NH Black | Hispanic | Marshallese | ||||||
|---|---|---|---|---|---|---|---|---|---|
| (n=65,800) | (n=1,680) | (n=21,654 ) | (n=2,488) | p | |||||
| n | % | n | % | n | % | n | % | ||
| Infant Sex | 0.13 | ||||||||
| Boys | 33,746 | 51.3 | 846 | 50.4 | 10,916 | 50.4 | 1,255 | 50.4 | |
| Girls | 32,053 | 48.7 | 834 | 49.6 | 10,738 | 49.6 | 1,233 | 49.6 | |
| Infant Birthweight | <0.01 | ||||||||
| <1500 grams | 520 | 0.8 | 49 | 2.9 | 179 | 0.8 | 33 | 1.3 | |
| 1500–2499 grams | 2,933 | 4.5 | 135 | 8.1 | 994 | 4.6 | 189 | 7.6 | |
| 2500–4000 grams | 55,552 | 84.5 | 1,401 | 83.6 | 18,691 | 86.4 | 2,173 | 87.4 | |
| >4000 grams | 6,750 | 10.3 | 91 | 5.4 | 1,767 | 8.2 | 92 | 3.7 | |
| Infant Gestational Age | <0.01 | ||||||||
| <32 weeks | 725 | 1.2 | 50 | 3.2 | 281 | 1.4 | 59 | 2.7 | |
| 32–36 weeks | 5,263 | 8.3 | 162 | 10.2 | 1,953 | 9.4 | 427 | 19.3 | |
| ≥37 weeks | 57,150 | 90.5 | 1,372 | 86.6 | 18,482 | 89.2 | 1,732 | 78.1 | |
| Fetal Growth | <0.01 | ||||||||
| Small for gestational age | 5,596 | 8.9 | 252 | 15.9 | 1,914 | 9.3 | 335 | 15.1 | |
| Appropriate for gestational age | 50,107 | 79.4 | 1,213 | 76.7 | 16,659 | 80.5 | 1,746 | 78.8 | |
| Large for gestational age | 7,404 | 11.7 | 116 | 7.3 | 2,130 | 10.3 | 136 | 6.1 | |
| Abnormal Conditions of Newborn | |||||||||
| Anemia (Hct <39/Hgb <13) | 257 | 0.4 | 11 | 0.7 | 123 | 0.6 | 24 | 1.0 | <0.01 |
| Birth injury | 629 | 1.0 | 12 | 0.7 | 168 | 0.8 | 38 | 1.5 | <0.01 |
| Hyaline membrane disease/RDS | 1,123 | 1.7 | 39 | 2.3 | 333 | 1.5 | 75 | 3.0 | <0.01 |
| Meconium aspiration syndrome | 124 | 0.2 | 5 | 0.3 | 60 | 0.3 | 9 | 0.4 | <0.05 |
| Assisted ventilation <30 minutes | 978 | 1.5 | 30 | 1.8 | 310 | 1.4 | 85 | 3.4 | <0.01 |
| Assisted ventilation ≥30 minutes | 651 | 1.0 | 17 | 1.0 | 200 | 0.9 | 28 | 1.1 | 0.72 |
| Seizures | 42 | 0.1 | 1 | 0.1 | 8 | 0 | 2 | 0.1 | 0.51 |
| Other abnormal conditions of infant | 1,564 | 2.4 | 45 | 2.7 | 457 | 2.1 | 114 | 4.6 | <0.01 |
| Baby transferred to ICU | 1,744 | 2.7 | 75 | 4.5 | 461 | 2.1 | 74 | 3.0 | <0.01 |
NH=Non-Hispanic; Hct: hematocrit; Hgb: hemoglobin
After adjusting for covariates in multivariable regression analyses, infants born to Marshallese women experienced greater adverse outcomes compared to NH whites (Table 6). Marshallese infants had a slightly higher prevalence of low birthweight (PR=1.12; 95% CI: 0.96, 1.29), preterm birth (PR= 1.66; 95% CI: 1.50, 1.83), and small-for-gestational age (PR=1.25; 95% CI: 1.12, 1.39) compared to NH white infants. Marshallese infants were less likely to be macrosomic or large-for-gestational age (OR= 0.43; 95% CI: 0.35, 0.53 and OR=0.59: 95% CI: 0.50, 0.70, respectively). Marshallese infants were more likely to have anemia (PR=3.10; 95% CI: 2.01, 4.77), birth injury (PR=2.13; 95% CI: 1.50, 3.03), and hyaline membrane disease or respiratory distress syndrome (PR=1.26; 95% CI: 0.99, 1.60) compared to NH white infants. Marshallese infants were also more likely to have meconium aspiration syndrome (PR=2.09; 95% CI: 0.97, 4.53), require assisted ventilation for <30 minutes (PR=2.11; 95% CI: 1.64, 2.71), and have “other abnormal conditions of the infant” (PR=1.73; 95% CI: 1.42, 2.12).
Table 6.
Prevalence of Infant Outcomes by Maternal Race/Ethnicity, Benton and Washington Counties, Arkansas, 1997–2013
| NH White | NH Black | Hispanic | Marshallese | ||||||
|---|---|---|---|---|---|---|---|---|---|
| (n=65,800) | (n=1,680) | (n=21,654 ) | (n=2,488) | p | |||||
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | ||
| Mean Birthweight (grams) | 3,373 | 554 | 3134 | 637.8 | 3329 | 538.8 | 3,110 | 528.6 | <0.01 |
| Mean gestational age (weeks) | 38.9 | 2.3 | 38.4 | 2.7 | 38.8 | 2.4 | 38.1 | 2.9 | <0.01 |
| Apgar Scores | |||||||||
| 1 minute Apgar score | 7.8 | 1.2 | 7.7 | 1.4 | 7.8 | 1.2 | 7.6 | 1.4 | <0.01 |
| 5 minute Apgar score | 8.9 | 0.7 | 8.8 | 0.9 | 8.9 | 0.7 | 8.8 | 0.9 | <0.01 |
DISCUSSION
Information about pregnancy and infant outcomes among Marshallese women in the US is scarce. The intent of our study was to provide data to aid clinicians in caring for and counseling Marshallese women on perinatal risks and to determine if Marshallese women and infants have increased risk of specific adverse perinatal outcomes. In this study, Marshallese women did not have a higher prevalence of identified medical risk factors included on the birth certificate, but had higher prevalence of the category “other medical risk factors” that complicated their pregnancies. Their use of tobacco and alcohol during pregnancy was much lower than NH white women. In general, lower percentages of Pacific Islander women access first trimester prenatal care and Marshallese women had a similar pattern of low prenatal care usage. Although Marshallese immigrants are legally able to live and work in the US, they are not eligible for Medicaid or Medicaid expansion benefits.(McElfish et al., 2015) Lack of health insurance may explain low first trimester prenatal care rates for Marshallese women. In addition, sociodemographic barriers (e.g. not speaking or understanding English), socioecological constraints, and low trust of Western medicine may inhibit use of healthcare by immigrant Marshallese women.(Ayers et al., 2018) We found higher rates of cesarean deliveries and other obstetric interventions including the use of forceps and vacuum-assisted delivery. Our study also showed that Marshallese infants were more likely be low birthweight, preterm, and small-for-gestational age compared to NH white infants.
The only study to date that examined obstetric outcomes among the Marshallese population separate from other Pacific Islander populations found similar results.(Schempf et al., 2010) Schempf et al. (2010)(Schempf et al., 2010) used California data from 2003–2005 on several subgroups of Pacific Islanders including 938 Marshallese women; 18.8% of Marshallese infants were preterm and 8.4% were low birthweight. Marshallese infants were two times more likely to be preterm and 1.38 times more likely to be low birthweight. They also found low first trimester prenatal care rates and low rates of prenatal cigarette smoking.
A few studies have investigated obstetric outcomes among all Pacific Islanders combined and among Pacific Islander subgroups. Rao et al. (2006) found that Pacific Islander women (Tongan, Samoan, Guamanian, and Polynesian combined) did not have statistically significantly higher rates of preterm birth or low birthweight but did have statistically significantly higher rates of gestational diabetes, gestational hypertension, cesarean deliveries, and macrosomia.(Rao et al., 2006) Native Hawaiian women are reported to have higher rates of low birthweight,(Chang et al., 2015; Todd & Peabody, 2004) preterm birth,(Schempf et al., 2010) gestational diabetes,(Chang et al., 2015) and cesarean deliveries.(Wong et al., 2008) Samoan women have higher rates of macrosomia,(Chang et al., 2015; Tsitas et al., 2015; Wong et al., 2008) preterm birth,(Schempf et al., 2010; Wong et al., 2008) very preterm birth (<32 weeks),(Wong et al., 2008) gestational diabetes,(Chang et al., 2015) pregnancy-associated hypertension,(Chang et al., 2015) cesarean section,(Wong et al., 2008) and eclampsia.(Wong et al., 2008) The three studies which investigated obstetric outcomes among Guamanian women report higher rates of low birthweight,(Wong et al., 2008) preterm birth,(Schempf et al., 2010; Wong et al., 2008) very preterm birth,(Wong et al., 2008) gestational diabetes,(Schempf et al., 2010) pregnancy-associated hypertension,(Chang et al., 2015) cesarean section,(Wong et al., 2008) and eclampsia(Wong et al., 2008) Only one study reported obstetric outcomes for women from Micronesia and showed higher rates of pregnancy-associated hypertension and cesarean section compared to Caucasian women.(Schempf et al., 2010)
Taken together, the literature reveals that each Pacific Islander subgroup has different perinatal risk profiles and that Marshallese women may have distinct perinatal outcomes from other Pacific Islander subgroups. Unlike findings for Native Hawaiian, Samoan, and Guamanian women and all Pacific Islander women combined, Marshallese women in our population did not have higher rates of gestational diabetes, pregnancy-associated hypertension or eclampsia. In contrast to Samoans, all Pacific Islanders combined and “other Pacific Islanders,” we found no evidence of higher rates of macrosomia or large-for-gestational age for Marshallese infants. Thus, extrapolating perinatal findings from studies which combine all Pacific Islanders in aggregate or from other Pacific Islander populations seems to be inappropriate.
A few potential limitations should be considered when evaluating the results of our study. First, although our study population consisted of the largest Marshallese study population to date and the largest population in the continental US, fewer than 3,000 live births occurred to Marshallese women during the study period. Second, to ensure the data set included Marshallese, records where selected if they included both Pacific Islander as their race and the mother reported being born in the Marshall Islands. Therefore, we may have under-ascertained live births to Marshallese women and underestimation of the true prevalence of their outcomes. Third, we relied on information about maternal risk factors, pregnancy complications, and infant outcomes from the birth certificates instead of medical records. Studies indicate that the accuracy of reporting of these conditions on birth certificates varies greatly, and these conditions are often underreported or inaccurately reported on birth certificates in comparison to medical records.(Schempf et al., 2010) Forth, we were unable to control for the amount of time mothers have lived in the US, acculturation, immigration status, obesity, and other factors that may affect care. Despite these limitations, our study has several strengths. Our study population included almost 2,500 singleton Marshallese births, which is the largest study of Marshallese births to date. Unlike other studies, which aggregate all Pacific Islander populations, our study focused solely on Marshallese women and compared birth outcomes to those of NH black and Hispanics within the same county. Our study also provided a broader examination of perinatal outcomes by including all conditions reported on the standard US birth certificate, as opposed to the few selected conditions reported in other studies. Our results highlight the heterogeneity in perinatal outcomes among expatriate women from the Pacific Islands and can assist clinicians who care for and counsel Marshallese women.
Table 7.
Prevalence Rates (PR) and 95% Confidence Intervals (CI) for Infant Outcomes by Maternal Race/Ethnicity, Benton and Washington Counties, Arkansas, 1997–2013
| NH-Black | Hispanic | Marshallese | ||||
|---|---|---|---|---|---|---|
| (n=1,680) | (n=21,654 ) | (n=2,488 ) | ||||
| PR (95% CI) | PR* (95% CI) | PR (95% CI) | PR* (95% CI) | PR (95% CI) | PR* (95% CI) | |
| Infant Sex | ||||||
| Boys | 0.98 (0.94–1.03) | 0.99 (0.94–1.04) | 0.98 (1.03–0.97) | 0.98 (0.97–1.00) | 0.99 (0.97–0.99) | 1.00 (0.96–1.04) |
| Girls | 1.02 (0.97–1.07) | 1.01 (0.97–1.06) | 1.02 (1.07–1.00) | 1.02 (1.00–1.04) | 1.02 (1.00–1.04) | 1.00 (0.96–1.05) |
| Infant Birthweight | ||||||
| <1500 grams | 3.59 (2.82–4.57) | 3.18 (2.46–4.12) | 0.89 (4.57–0.77) | 0.67 (0.55–0.82) | 1.46 (0.77–1.04) | 1.03 (0.72–1.46) |
| 1500–2499 grams | 1.75 (1.52–2.02) | 1.69 (1.46–1.96) | 0.96 (2.02–0.90) | 0.85 (0.78–0.92) | 1.42 (0.90–1.02) | 1.12 (0.96–1.29) |
| 2500–4000 grams | 0.97 (0.95–0.99) | 0.97 (0.95–0.99) | 1.03 (1.02–1.04) | 1.03 (1.03–1.04) | 1.04 (1.02–1.06) | 1.05 (1.03–1.07) |
| >4000 grams | 0.52 (0.43–0.64) | 0.57 (0.46–0.69) | 0.80 (0.76–0.84) | 0.84 (0.79–0.89) | 0.37 (0.30–0.45) | 0.43 (0.35–0.53) |
| Infant Gestational Age | ||||||
| <32 weeks | 2.94 (2.34–3.70) | 2.60 (2.04–3.32) | 0.99 (3.70–0.87) | 0.77 (0.66–0.91) | 1.82 (0.87–1.12) | 1.25 (0.94–1.65) |
| 32–36 weeks | 1.23 (1.08–1.41) | 1.19 (1.04–1.37) | 1.07 (1.41–1.02) | 0.97 (0.92–1.03) | 1.91 (1.02–1.12) | 1.66 (1.50–1.83) |
| ≥37 weeks | 0.92 (0.90–0.94) | 0.95 (0.93–0.97) | 0.99 (0.94–0.98) | 1.01 (1.00–1.01) | 0.81 (0.98–1.00) | 0.90 (0.88–0.92) |
| Fetal Growth | ||||||
| Small for gestational age | 1.73 (1.55–1.93) | 1.72 (1.54–1.92) | 1.02 (1.93–0.97) | 0.84 (0.79–0.90) | 1.48 (0.97–1.07) | 1.25 (1.12–1.39) |
| Appropriate for gestational age | 0.94 (0.91–0.97) | 0.96 (0.93–0.98) | 1.01 (0.97–1.00) | 1.04 (1.03–1.05) | 0.93 (1.00–1.02) | 1.02 (1.00–1.05) |
| Large for gestational age | 0.60 (0.50–0.72) | 0.65 (0.55–0.78) | 0.88 (0.72–0.84) | 0.89 (0.84–0.93) | 0.50 (0.84–0.92) | 0.59 (0.50–0.70) |
| Abnormal Conditions of Newborn | ||||||
| Anemia (Hct <39/Hgb <13) | 1.85 (1.06–3.22) | 1.89 (1.08–3.29) | 1.44 (1.17–1.78) | 1.18 (0.92–1.52) | 2.60 (1.74–3.88) | 3.10 (2.01–4.77) |
| Birth injury | 0.72 (0.41–1.27) | 0.69 (0.38–1.24) | 0.81 (0.68–0.96) | 0.83 (0.68–1.02) | 1.64 (1.19–2.26) | 2.13 (1.50–3.03) |
| Hyaline membrane disease/RDS | 1.37 (1.04–1.81) | 1.27 (0.96–1.68) | 0.86 (0.77–0.96) | 0.79 (0.69–0.91) | 1.55 (1.24–1.93) | 1.26 (0.99–1.60) |
| Meconium aspiration syndrome | 1.55 (0.63–3.78) | 1.57 (0.64–3.85) | 1.48 (1.09–2.01) | 1.35 (0.93–1.96) | 1.95 (0.99–3.83) | 2.09 (0.97–4.53) |
| Assisted ventilation <30 minutes | 1.39 (1.01–1.91) | 1.43 (1.04–1.98) | 0.96 (0.85–1.09) | 0.92 (0.79–1.07) | 2.23 (1.80–2.76) | 2.11 (1.64–2.71) |
| Assisted ventilation ≥30 minutes | 1.06 (0.70–1.61) | 0.97 (0.61–1.52) | 0.87 (0.75–1.01) | 0.72 (0.60–0.87) | 1.08 (0.76–1.53) | 0.92 (0.63–1.35) |
| Seizures | 0.83 (0.11–6.02) | 0.86 (0.12–6.43) | 0.67 (0.34–1.33) | 0.68 (0.31–1.50) | 1.17 (0.28–4.82) | 1.39 (0.33–5.75) |
| Other abnormal conditions of infant | 1.27 (0.98–1.65) | 1.13 (0.86–1.50) | 0.86 (0.78–0.95) | 0.76 (0.67–0.86) | 1.87 (1.56–2.24) | 1.73 (1.42–2.12) |
| Baby transferred to ICU | 1.07 (0.93–1.24) | 1.65 (1.34–2.02) | 0.62 (0.58–0.66) | 0.68 (0.60–0.76) | 0.53 (0.44–0.63) | 0.85 (0.67–1.07) |
NH=Non-Hispanic; PR=Prevalence Ratio; Hct: hematocrit; Hgb: hemoglobin
Adjusted by maternal age, education, parity, and marital status
Acknowledgments:
The authors would like to thank Robin Richardson and Lindsey Overman for assisting with the preparation of this manuscript.
Funding
This study was supported by the CDC National Center for Birth Defects and Developmental Disabilities (#5U01DD000491-05), the Arkansas Biosciences Institute (#037062), and the Translational Research Institute grant (1U54TR001629-01A1) through the National Center for Advancing Translational Sciences of the National Institutes of Health (NIH).
“The content is solely the responsibility of the authors and does not necessarily represent the official views of the Centers for Disease Control and Prevention or the National Institutes of Health.”
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