Gestational diabetes mellitus and time in active labor: A population‐based cohort study

Abstract

Introduction

Women with gestational diabetes mellitus (GDM) have higher rates of adverse perinatal outcomes compared with women without GDM, including an increased risk for having labor induced and for cesarean section. The findings from previous studies analyzing duration of labor in women with GDM are contradictory.

The aim of the study was to evaluate the impact of GDM on time in spontaneous and induced active labor.

Material and methods

This was a population‐based cohort study including 247 524 primiparous women who gave birth to a singleton fetus with cephalic presentation, ≥34⁺⁰ (completed gestational weeks + additional days) between January 2014 and May 2020 in Sweden. Data was obtained from the Swedish Pregnancy Register. Time in active labor was compared between women with GDM and without GDM with a spontaneous labor onset or induction of labor using Kaplan Meier survival analysis and Cox regression analysis.

Results

Women with GDM had significantly longer time in active labor, both with a spontaneous onset and induction of labor compared to women without GDM. Women with GDM had a decreased chance of vaginal delivery at a certain time‐point compared to women without GDM, with adjusted hazard ratio of 0.92 (0.88–0.96) and 0.83 (0.76–0.90) for those with spontaneous onset and induction of labor, respectively. Women with GDM had increased risk for time in active labor ≥12 h both in spontaneous labor onset (adjusted odds ratio 1.14 [1.04–1.25]) and in induction of labor (adjusted odds ratio 1.55 [1.28–1.87]).

Conclusions

Women with GDM seem to spend a longer time in active labor, both in spontaneous and induced active labor compared to women without GDM. To be able to individualize care intrapartum, there is a need for more studies demonstrating the impact of hyperglycemia during pregnancy on outcomes during childbirth.

Women with gestational diabetes mellitus spend a longer time in active labor compared to women without gestational diabetes, both in spontaneous and in induced labor.

Abbreviations

aOR

adjusted odds ratio

BMI

body mass index

CS

cesarean section

GDM

gestational diabetes mellitus

IOL

induction of labor

IQR

interquartile range

LGA

large for gestational age

OGTT

oral glucose tolerance test

SPR

Swedish Pregnancy Register

WHO

World Health Organization

1. INTRODUCTION

Gestational diabetes mellitus (GDM) is one of the most common complications during pregnancy with the prevalence rising worldwide. ¹ The International Diabetes Federation estimates that one in six live births (16.8%) are to women with some type of hyperglycemia in pregnancy, and the majority (84%) are related to GDM. ² , ³ GDM is a heterogeneous condition and the mode of screening, the diagnostic criteria and the clinical management of GDM vary greatly worldwide and also within Sweden. ⁴ , ⁵ , ⁶

Women with GDM have higher rates of adverse maternal and perinatal outcomes compared to women without GDM. The risks include pre‐eclampsia, shoulder dystocia, having a large for gestational age (LGA) baby, induction of labor (IOL) and both emergency and elective cesarean sections (CS). ⁵ , ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ The pathophysiological mechanisms underlying the increased risk for CS are not fully understood, but some studies have suggested that it may be due to the confounding factor of obesity while others have found diabetes to be an independent risk factor. ¹¹ , ¹²

Fetal distress and macrosomia also contribute to the overall increased emergency CS rate, but studies on women with GDM ¹³ and studies including both women with pre‐pregnancy diabetes and GDM ¹² show that a reduction in macrosomia does not result in a corresponding reduced CS rate.

The findings from previous studies analyzing duration of labor in women with GDM are contradictory. Some studies show similar active labor progress in women with GDM compared to women without GDM. ¹⁴ , ¹⁵ On the other hand, Sheiner et al. ¹⁶ noted that GDM was an independent risk factor for failure of labor to progress during the first stage. In vitro studies on myometrium from humans ¹⁷ and from mice ¹⁸ comparing individuals with and without diabetes (both pre‐pregnancy diabetes and GDM) suggest that diabetes may lead to changes in the myometrium reflecting impaired uterine contractility. Hence, a dysfunctional myometrium and/or labor could be a contributing factor to some adverse outcome seen in women with GDM. Therefore, population‐based studies are needed to thoroughly assess duration of labor in women with GDM and the impact of hyperglycemia during pregnancy on outcomes during childbirth to enable an optimized and individualized obstetric management of this growing high risk‐group of women.

We hypothesized that women with GDM would have a longer time in active labor compared with women without GDM.

The aim of this study was therefore to evaluate the impact of gestational diabetes on time in active labor, in both women with spontaneous onset and induced labor.

2. MATERIAL AND METHODS

In this population‐based cohort study, data was obtained from the Swedish Pregnancy Register (SPR). The SPR is a national quality register established in 2013. The register collects data on pregnancy and childbirth, from the first visit at the antenatal care clinic to the follow‐up visit, which usually occurs around 6–12 weeks postpartum. The SPR contains information on maternal characteristics, pregnancy complications, and data on labor and birth. In 2020, 97.9% of all deliveries in Sweden were registered in the SPR. The coverage rate in 2014 was 85%. The majority of the variables included in the register are continuously transferred electronically from the medical antenatal and labor records. Some variables are registered manually by the midwives at the antenatal care clinics. ¹⁹

During the study period between January 1, 2014 and May 30, 2020, 247 524 primiparous women delivered a singleton fetus, ≥34⁺⁰ (completed gestational weeks + additional days) with cephalic presentation, and had their data available in the SPR.

To obtain the population for inclusion in the analysis of time in active labor, we first excluded women with other types of diabetes than GDM (eg pre‐pregnancy diabetes) and women delivered by elective CS. Data were then restricted to primiparae with trial of labor (women with emergency section were included). We then excluded women who had missing value or faulty data on start of active labor to achieve a sample of primiparous women going in to trial of labor with valid data concerning the start of active labor. A flowchart of how the study population was derived in seen in Figure 1.

FIGURE 1.

Flow chart of the study population.

The maternal variables assessed for the present study were GDM, age at delivery, country of birth, education level, body mass index (BMI) in early pregnancy, gestational weight gain, smoking in early pregnancy, support for fear of childbirth during pregnancy, treatment for psychiatric disorder during pregnancy, hypertension, pre‐eclampsia and gestational age at delivery. Gestational age was calculated using the estimated date of delivery by early second trimester ultrasound, offered to all women in antenatal care and free of charge; however, when ultrasound estimation was missing, the first day of the last menstrual period was used.

The delivery and birth variables assessed were labor onset type (spontaneous or induction), the time of start of contractions, the time of start of the active phase of labor, the time of delivery, usage of epidural anesthesia, usage of oxytocin, fetal presentation (crown, occiput posterior or other), instrumental delivery (vacuum extraction/forceps), mode of delivery (non‐instrumental vaginal delivery, instrumental delivery, CS), birthweight, small for gestational age and LGA. Small for gestational age was defined as birthweight below two standard deviations in relation to gestational week and sex using Swedish growth charts and LGA was defined as birthweight above two standard deviations in relation to gestational week and sex using the Swedish growth charts. ²⁰

A definition of how all the different variables were extracted is presented in Table S1. GDM was defined as hyperglycemia diagnosed for the first time in pregnancy but did not meet the criterion for diabetes during the non‐pregnant state. Different diagnostic criteria for the diagnosis of GDM were used in Sweden during the study period, both the recommended guidelines from the World Health Organization (WHO) from 2013 ³ (≥5.1 mmol/L in fasting and/or ≥ 10.0 mmol/L 1 h after a 75 g oral glucose tolerance test [OGTT] and/or ≥8.5 mmol/L 2 h after OGTT) as well as the older guidelines from 1999 (≥7.0 mmol/L in fasting or ≥ 10.0 mmol/L 2 h after OGTT). ⁹ Until 2018, only the older guidelines from 1999 were used for the diagnosis of GDM in Sweden. During 2018, 65% of the pregnant population were subject to the new recommended guidelines from 2013 within an ongoing study; ²¹ however, during 2019–2021, only about one third of regions in Sweden were using the 2013 WHO guidelines. ¹⁹ The mode of screening for GDM (using risk factor based or universal screening) and cutoffs for diagnosis varied throughout the country during the study period. One region in Sweden (Skåne), which had 13.3% of the deliveries in Sweden 2016, ²² used universal screening and only capillary sampling whereas in the rest of Sweden the use of capillary or venous sampling varied.

Time in active labor was defined as the time between the start of active labor until the time of delivery. The start of active labor was, during the first part of the study period (January 2014–March 2015), defined as a cervix dilated 3 cm or more in women with painful regular uterine contractions. During the remainder of the study period, the onset of active labor was defined according to the Swedish nationally recommended definition, which states that at least two out of three of the following criteria must be fulfilled: spontaneous rupture of the membrane, regular painful contractions (2–3/10 min), and a cervix dilated 4 cm or effaced and dilated more than 1 cm. In addition to these criteria, the labor should progress within the subsequent 2 h. ²³

Time in active labor was compared between women with GDM and women without GDM. Women with spontaneous onset of labor and women with induced labor were analyzed separately.

2.1. Statistical analyses

Categorical data is presented as number and percent. Continuous, not normally distributed, data is presented as median with quartiles and interquartile ranges (IQR). The descriptive, overall differences in time in active labor between women with GDM and no GDM for spontaneous onset of labor and induction of labor were evaluated using the Mann Whitney U test.

Kaplan Meier survival analyses were performed, and graphs were produced to illustrate the association between GDM and time in active labor, taking censoring due to emergency CS into account when applicable. Women with spontaneous labor onset and women with induced labor were analyzed separately.

Cox regression analyses were performed, and graphs were produced to illustrate the association between GDM and time in active labor taking censoring due to emergency CS into account (when applicable) and adjusting for confounding factors. Several factors were considered possible confounders and were assessed using a directed acyclic graph (Figure S1).

Confounding factors that were adjusted for included maternal BMI in early pregnancy, smoking in early pregnancy, maternal age at delivery and gestational week at delivery. Birthweight was considered a mediator. Furthermore, the impact of maternal height was evaluated.

From the Cox regression analyses, we calculated the hazard ratio (HR) and adjusted hazard ratio (aHR) for the risk of an event, that is, vaginal delivery at a specific time‐point. Women with spontaneous labor onset and induction of labor (IOL) were analyzed separately. Multivariable logistic regression analyses were used to estimate the crude (OR) and adjusted (aOR) odds ratio for time in active labor ≥12 h compared with <12 h in women with or without GDM. In the multivariable analyses, adjustments were made for BMI, maternal age at delivery, smoking and gestational week at time of delivery.

Drop‐out analyses in trial of labor deliveries were made to compare women with and without available data on the start of active labor. Chi‐2 analyses were used to calculate the overall heterogeneity within each domain.

The statistical analyses were performed using IBM SPSS version 28 (IBM Inc., Armonk, NY, USA). A p‐value <0.05 was considered statistically significant. Data were obtained from the SPR and deidentified, with no direct participation of patients; hence, informed consent was waived.

2.2. Ethics statement

This study was approved by the Regional Ethical Review Board in Linköping, Sweden (2018/464–31) on November 6, 2018.

3. RESULTS

A total of 172 380 women were included in the final study population for analyses of time in active labor, and 2978 (1.7%) of these women had GDM. More women with GDM were obese, had induced labor and gave birth to an LGA infant compared to women without GDM. Maternal, labor and neonatal characteristics are presented in Table 1.

TABLE 1.

Maternal, labor and neonatal characteristics of trial of labor deliveries N = 172 380.

	Gestational diabetes mellitus n = 2978		No gestational diabetes mellitus n = 169 402
	n	(%)	n	(%)
Age (years)
<20	37	(1.2)	3625	(2.1)
20–34	2453	(82.4)	148 054	(87.4)
35–39	391	(13.1)	15 024	(8.9)
≥40	97	(3.3)	2660	(1.6)
Age unknown	0	(0.0)	39	(0.0)
Country of birth	1719	(57.7)	120 737	(71.3)
Nordic countries
Other European and USA	211	(7.1)	10 953	(6.5)
Remaining/other countries	1048	(35.2)	37 712	(22.3)
Education level	46	(1.5)	1251	(0.7)
No schooling
≤9 years	222	(7.5)	7129	(4.2)
10–12 years	1137	(38.2)	54 207	(32.0)
University	1143	(38.4)	79 604	(47.0)
Education level unknown	430	(14.4)	27 211	(16.1)
BMI (kg/m2)	44	(1.5)	4908	(2.9)
<18.5
18.5–24.9	964	(32.4)	96 556	(57.0)
25–29.9	725	(24.3)	34 937	(20.6)
30–34.9	495	(16.6)	10 967	(6.5)
≥35	496	(16.7)	4086	(2.4)
BMI unknown	254	(8.5)	17 948	(10.6)
Gestational weight gain (gwg)	907	(30.5)	40 173	(23.7)
Below recommended gwg
Within recommended gwg	721	(24.2)	46 183	(27.3)
Above recommended gwg	1096	(36.8)	65 098	(38.4)
Gestational weight gain unknown	254	(8.5)	17 948	(10.6)
Smoking in early pregnancy	2674	(89.8)	151 347	(89.3)
No
Yes	148	(5.0)	6498	(3.8)
Smoking habits unknown	156	(5.2)	11 557	(6.8)
Support for fear of childbirth during pregnancy	131	(4.4)	6788	(4.0)
Treated for psychiatric disorder during pregnancy	229	(7.7)	9961	(5.9)
Gestational age (weeks) at delivery	176	(5.9)	5616	(3.3)
34 + 0–36 + 6 w
37 + 0–39 + 6 w	1506	(50.6)	65 673	(38.8)
40 + 0–40 + 6 w	830	(27.9)	52 742	(31.1)
41 + 0–41 + 6 w	383	(12.9)	34 471	(20.3)
≥42 w	83	(2.8)	10 900	(6.4)
Pre‐eclampsia	50	(1.7)	1067	(0.6)
Occiput posterior position of fetal head	82	(2.8)	5187	(3.1)
Induction of labor	631	(21.2)	16 894	(10.0)
Emergency CS	210	(7.1)	6918	(4.1)
VE/forceps	387	(13.0)	19 035	(11.2)
Birthweight (g)	95	(3.2)	3868	(2.3)
< 2500 g
2500–3999 g	2439	(81.9)	143 272	(84.6)
≥ 4000 g	444	(14.9)	22 262	(13.1)
SGA	101	(3.4)	6191	(3.7)
LGA	216	(7.3)	3383	(2.0)

Abbreviations: BMI, body mass index; CS, cesarean section; g, grams; GWG, gestational weight gain according to the IOM (Institute of Medicine) recommendations; LGA, large for gestational age; SGA, small for gestational age; VE, vacuum extraction; W, weeks.

Drop‐out analyses and characteristics of the women who had missing data on the start of active labor are shown in Table S2.

Women with GDM had 0.9 h longer median time in active labor in IOL (7.92 h [IQR 4.68–11.96]) compared to women with no GDM (7.02 h [IQR 4.40–10.61 h]), p = 0.003. For women with a spontaneous onset of labor, there was no difference regarding median time in active labor between the groups (Table 2).

TABLE 2.

Time in active labor in women with and without gestational diabetes mellitus in trial of labor deliveries.

	All women n = 172 380					Women with spontaneous onset of labor n = 154 855					Women with induction of labor n = 17 525
	n	Quartiles (h)			Range (min‐max)	n	Quartiles (h)			Range (min‐max)	n	Quartiles (h)			Range (min‐max)
		25%	Median	75%			25%	Median	75%			25%	Median	75%
Women with GDM	2978	5.18	8.48	12.56	(0.17–61.23)	2347	5.33	8.65	12.76	(0.17–61.23)	631	4.68	7.92	11.96	(0.90–37.50)
Women without GDM	169 402	5.37	8.50	12.55	(0.12–70.51)	152 508	5.48	8.68	12.73	(0.12–70.51)	16 894	4.40	7.02	10.61	(0.13–70.43)

Abbreviation: GDM, gestational diabetes mellitus; h, hours.

Women with GDM had an increased risk for a time in active labor ≥12 h compared to women without GDM, both in spontaneous onset of labor (aOR 1.14 [1.04–1.25]), and in IOL (aOR 1.55 [1.28–1.87]) (Table 3).

TABLE 3.

Odds ratio for time in active labor ≥12 h in women with gestational diabetes mellitus vs women without gestational diabetes mellitus.

	Women with GDM n = 2978	Women without GDM n = 169 402	Crude odds ratio (95% CI)	Adjusted odds ratio a (95% CI)
Spontaneous labor onset n = 154 855	2347	152 508	1.04 (0.95–1.14)	1.14 (1.04–1.25)
Induction of labor n = 17 525	631	16 894	1.43 (1.19–1.72)	1.55 (1.28–1.87)

Abbreviations: CI, confidence interval; GDM, gestational diabetes mellitus.

^a Adjusted for maternal body mass index, maternal age, smoking in early pregnancy and gestational week at time of delivery.

In women with spontaneous onset of labor, the Kaplan Meier survival curves, taking censoring due to emergency CS into account (Figure S2A,B), showed no difference in duration of time in active labor between the women with or without GDM. In women with induced labor, the women with GDM had significantly longer duration of active labor (p = 0.002).

The Cox regression analyses, adjusted for confounders and taking censoring due to emergency CS into account, showed that women with GDM had a significantly longer time in active labor, both women with a spontaneous onset or induced labor (Figure 2A,B). Women with GDM had a decreased chance of vaginal delivery at a certain time‐point compared to women without GDM with aHR 0.92 (0.88–0.96) and aHR 0.83 (0.76–0.90) for those with spontaneous onset or induced labor, respectively. (Table 4) When including the mediator birthweight in the Cox regression analyses, the corresponding aHR figures were 0.94 (0.90–0.98) and 0.86 (0.79–0.94).

FIGURE 2.

(A) Cox regression analysis of time in active labor in women with gestational diabetes mellitus compared to women without gestational diabetes mellitus in spontaneous labor onset. Adjustments were made for maternal body mass index, maternal age, smoking in early pregnancy and gestational week at delivery. (B) Cox regression analysis of time in active labor in women with gestational diabetes mellitus compared to women without gestational diabetes mellitus in induction of labor. Adjustments were made for maternal body mass index, maternal age, smoking in early pregnancy and gestational week at delivery.

TABLE 4.

Hazard ratio and adjusted hazard ratio from Cox regression analyses of time in active labor in women with gestational diabetes mellitus compared to women without gestational diabetes mellitus.

	Women with GDM n = 2978	Women without GDM n = 169 402	Crude hazard ratio (95% CI)	Adjusted hazard ratio a (95% CI)
Spontaneous labor onset n = 154 855	2347	152 508	0.973 (0.933–1.014)	0.919 (0.880–0.958)
Induction of labor n = 17 525	631	16 894	0.876 (0.806–0.953)	0.828 (0.760–0.902)

Abbreviations: CI, confidence interval; GDM, gestational diabetes mellitus.

^a Adjustments were made for maternal body mass index, smoking in early pregnancy, maternal age and gestational week at delivery.

The impact of maternal height on the association of GDM and time in active labor was further evaluated and the corresponding aHR figures were 0.94 (0.90–0.98) and 0.86 (0.79–0.94) for spontaneous onset or induced labor, respectively.

4. DISCUSSION

Women with GDM seem to have a longer time in active labor, both in labor with spontaneous onset and in induced labor, after censoring for emergency CS and adjusting for relevant confounding factors compared to women without GDM. The difference was more prominent in women with induced labor. Furthermore, women with GDM have a significantly increased risk of a time in active labor of more than 12 h regardless of type of labor onset (spontaneous or induction) compared with women without GDM.

The strengths of this population‐based cohort study include the large dataset and the large number of primiparous women included for analysis of time in active labor. Furthermore, the study is nationwide, which adds diversity and implies that the results can be generalized to facilities with similar healthcare and socioeconomic conditions. Another strength is the methodology using Cox regression models, enabling adjustments for relevant confounding factors, and censoring for emergency CS instead of including only vaginal deliveries.

The SPR is a validated register that contains maternal pregnancy and labor data with a high coverage rate (97.9% of all deliveries in Sweden in 2020). ¹⁹ The detailed data on baseline evaluation of maternal comorbidity, socioeconomic factors and continuous registration of pregnancy complications enabled adjustments for possible confounding factors, such as maternal BMI in early pregnancy, which is a known factor that affects duration of labor. ²⁴

Although we adjusted our estimates for potentially important confounders, we cannot exclude the possibility that the adjusted estimates would be influenced by covariates not accounted for in the current analysis; for example, we were not able to adjust for glycemic control or type of medical treatment during pregnancy. The mode of treatment does not fully reflect the severity of hyperglycemia. For example, women with GDM with poor compliance to diet advice treatment could be considered for medical treatment as opposed to women with the same glycemic control but with perfect compliance to diet treatment. Also, the ICD‐10 code O24.4B does not state which kind of medical treatment (oral hypoglycemic or insulin) has been used. From this perspective, we wanted to evaluate the group with GDM, regarding time in active labor.

Women with GDM are a heterogeneous group in terms of being defined by different diagnostic criteria and experiencing various types of treatment, from dietary and physical activity advice to oral hypoglycemics and insulin. During the study period, there was no consensus regarding the diagnostic criteria for GDM in Sweden and different diagnostic criteria for GDM were used. ³ , ⁹ Further, a stepped wedged cluster randomized controlled trial, Changing Diagnostic Criteria for Gestational Diabetes (CDC4G) in Sweden (study protocol published), including 11 centers in Sweden, was also performed during the study period, with the aim of comparing pregnancy outcomes before and after the switch in GDM criteria. ²¹ In addition, the mode of screening (risk‐based or general) varied throughout the study period and across the country. It is possible that the results could have been different if all women were diagnosed with GDM using the same diagnostic criteria.

Hence, since the older diagnostic criteria were mostly used during the study period, the frequency of GDM may have been higher if the new guidelines had been introduced earlier, and this might explain the low prevalence of GDM in the present study population.

However, even in this heterogeneous group of women with GDM, receiving varying treatments and facing different diagnostic criteria, we were able to see a difference in time in active labor compared to women without GDM.

General limitations of large register studies are the risk of errors in recorded data and missing values. In the study population, after excluding the women with elective CS and pre‐pregnancy diabetes, 27.9% of the remaining women had missing data on the start of active labor and were therefore also excluded from the final study population. The characteristics of the population who had missing data on the start of active labor significantly differed from those who were included, but these differences were considered small from a clinical perspective and should probably not influence the results.

The definition of active labor was not the same during the study period, although in clinical practice there are no huge differences between these definitions of start of active labor. However, we cannot exclude the possibility that the different definitions influenced the results. Our definition of start of active labor may also affect the generalizability of the present study.

In a review article from 2016, Hanley et al. state that there is a lack of international consensus on what degree of cervical dilatation is necessary to indicate that active labor has begun. ²⁵ An American study has shown that latent labor may last until 6 cm cervical dilatation has occurred. ²⁶ Furthermore, WHO presented the Labor Care Guide (LCG) in 2020, introducing new intrapartum care guidelines which are believed to affect the management of labor worldwide. ²⁷

In studies examining both women with GDM and women with pre‐pregnancy diabetes, Hawkins et al. ¹⁴ examined progress and outcomes in 122 women with diabetes who underwent prostaglandin labor induction. They found that women with diabetes experienced significantly prolonged time to reach active labor and time to delivery and lower rates of delivery within 36 or 48 h due to a prolonged latent phase, but that the time in active labor was similar compared to women with no diabetes. In contrast to our findings, Timofeev et al. demonstrated that active labor progression and duration were similar in 458 nulliparous and 1079 multiparous women with pre‐existing diabetes mellitus and GDM compared to normal controls matched by neonatal birthweight, parity and maternal BMI. ¹⁵ However, only vaginal deliveries with normal neonatal outcome were included.

When examining only women with GDM, Sheiner et al. compared obstetric risk factors for failure to progress in the first (1197 women) vs the second stage (1154 women) of labor and noted that GDM was an independent risk factor for failure of labor to progress during the first stage. ²⁸

Looking at the aspect of LGA on time in active labor, Blankenship et al. ²⁹ showed that the time required to reach the second stage of labor was longer in women with LGA infants compared to those with appropriate‐for‐gestational age infants. In this retrospective cohort study, 17 097 women were included and 1254 (7.3%) had an LGA infant. The presence of pre‐pregnancy diabetes and GDM had no apparent effect on the time in labor in this study.

There are a few studies on diabetes and duration of labor, with varying results as seen above. Since most of these studies include both women with GDM and women with pre‐pregnancy diabetes the results are more difficult to interpret. In addition, none of the available studies include emergency CS in the analysis which may have led to selection bias.

To the best of our knowledge, this is the first study analyzing a national cohort of primiparous women with GDM where women with spontaneous onset and IOL were analyzed separately and emergency cesareans were included.

The underlying mechanisms behind a possible longer duration of labor in women with GDM irrespective of labor onset can only be speculated upon. Al Qathani et al. studied myometrial contractility on lower uterine segment biopsies from women with and without diabetes (both pre‐pregnancy diabetes and GDM) undergoing elective CS. They found that women with diabetes had less uterine muscle mass, reduced calcium channel expression, reduced intracellular calcium and a decreased contraction amplitude and duration in vitro, which may be translated into inferior uterine contractility. The authors conclude that these factors significantly contribute to the increased emergency CS rate in patients with diabetes. ¹⁷

An alternative possibility is that metabolic disturbances associated with diabetes, such as hyperglycemia, may impede labor progression by affecting arachidonic acid metabolism. Hyperglycemia is known to affect levels of arachidonic acid, as well as several prostaglandin metabolites, and these derangements in arachidonic acid metabolism are associated with embryopathy. ³⁰ , ³¹ , ³² Regulation of arachidonic acid metabolism is thought to be critical for labor progression, ³³ with differential expression during gestation and parturition for arachidonic acid and its prostaglandin metabolites.

5. CONCLUSION

Women with GDM seem to have a longer time in active labor, both in spontaneous labor onset and in IOL compared to women without GDM. To be able to individualize care intrapartum, there is a need for more studies demonstrating the impact of hyperglycemia during pregnancy on outcomes during childbirth. Future studies will show whether the difference in time in active labor between women with GDM and those without GDM found in the present study persists with new definitions of active labor as well as labor progression.

AUTHOR CONTRIBUTIONS

SN, MB and KK designed and planned the study. KK and SN performed the statistical analyses. SN, MB, KK, SC, and CL contributed to the analysis and interpretation of data for the work. SN wrote the manuscript. MB, KK, CL and SC critically revised the manuscript. All authors gave final approval and agreed to be accountable for all aspects of work ensuring integrity and accuracy.

FUNDING INFORMATION

This study was supported by ALF Grants RÖ‐792621, Region Östergötland, Sweden and the Medical Research Council of Southeast Sweden (FORSS; grant no. FORSS‐904141).

CONFLICT OF INTEREST STATEMENT

The authors confirm there are no conflicts of interest.

Supporting information

Figure S1.

Figure S2.

Table S1.

Table S2.

Nevander S, Carlhäll S, Källén K, Lilliecreutz C, Blomberg M. Gestational diabetes mellitus and time in active labor: A population‐based cohort study. Acta Obstet Gynecol Scand. 2023;102:873‐882. doi: 10.1111/aogs.14592