The effect of mode of delivery and duration of labour on subsequent pregnancy outcomes: a retrospective cohort study

The association between unintended hysterotomy extensions with cesarean delivery and subsequent preterm birth

BACKGROUND

An increased risk for preterm birth has been observed among individuals with a previous second stage cesarean delivery when compared with those with a previous vaginal delivery. One mechanism that may contribute to the increased risk for preterm birth following a second stage cesarean delivery is the increased risk for cervical injury because of extension of the uterine incision (hysterotomy) into the cervix. The contribution of hysterotomy extension to the rate of preterm birth in a subsequent pregnancy has not been investigated and may shed light on the mechanism underlying the observed relationship between the mode of delivery and subsequent preterm birth.

OBJECTIVE

We aimed to quantify the association between unintended hysterotomy extension and preterm birth in a subsequent delivery.

STUDY DESIGN

We performed a retrospective cohort study using electronic perinatal data collected from 2 university-affiliated obstetrical centers. The study included patients with a primary cesarean delivery of a term, singleton live birth and a subsequent singleton birth in the same catchment (2005-2021). The primary outcome was subsequent preterm birth <37 weeks' gestation; secondary outcomes included subsequent preterm birth at <34, <32, and <28 weeks' gestation. We assessed crude and adjusted associations between unintended hysterotomy extensions and subsequent preterm birth with log binomial regression models using rate ratios and 95% confidence intervals. Adjusted models included several characteristics of the primary cesarean delivery such as maternal age, length of active labor, indication for cesarean delivery, chorioamnionitis, and maternal comorbidity.

RESULTS

A total 4797 patients met the study inclusion criteria. The overall rate of unintended hysterotomy extension in the primary cesarean delivery was 6.0% and the total rate of preterm birth in the subsequent pregnancy was 4.8%. Patients with an unintended hysterotomy extension were more likely to have a longer duration of active labor, chorioamnionitis, failed vacuum delivery attempt, second stage cesarean delivery, and persistent occiput posterior position of the fetal head in the primary cesarean delivery and higher rates of smoking in the subsequent pregnancy. Multivariable analyses that controlled for several confounders showed that a history of hysterotomy extension was not associated with a higher risk for preterm birth <37 weeks' gestation (adjusted rate ratio, 1.55; 95% confidence interval, 0.98-2.47), but it was associated with preterm birth <34 weeks' gestation (adjusted rate ratio, 2.49; 95% confidence interval, 1.06-5.42).

CONCLUSION

Patients with a uterine incision extension have a 2.5 times higher rate of preterm birth <34 weeks' gestation when compared with patients who did not have this injury. This association was not observed for preterm birth <37 weeks' gestation. Future research should aim to replicate our analyses with incorporation of additional data to minimize the potential for residual confounding.

Operative delivery in the second stage of labor and preterm birth in a subsequent pregnancy: a systematic review and meta-analysis

OBJECTIVE

This study aimed to quantify the association between mode of operative delivery in the second stage of labor (cesarean delivery vs operative vaginal delivery) and spontaneous preterm birth in a subsequent pregnancy.

DATA SOURCES

MEDLINE, Embase, EmCare, CINAHL, the Cochrane Library, Web of Science: Core Collection, and Scopus were searched from database inception to April 1, 2023.

STUDY ELIGIBILITY CRITERIA

All retrospective cohort studies with participants who had a second-stage cesarean delivery (defined as intrapartum cesarean delivery at full cervical dilation) or operative vaginal delivery (including forceps- and/or vacuum-assisted delivery) and that reported the rate of preterm birth (either spontaneous or not specified) in subsequent pregnancy were included.

METHODS

Both a descriptive analysis and a meta-analysis were performed. A meta-analysis was performed for dichotomous data using the Mantel-Haenszel random-effects model and used the odds ratio as an effect measure with 95% confidence intervals. The risk of bias was assessed using Cochrane's 2022 Risk Of Bias In Non-randomized Studies of Exposure tool.

RESULTS

After screening 2671 articles from 7 databases, a total of 18 retrospective cohort studies encompassing 605,138 patients were included. The pooled rates of spontaneous preterm birth in a subsequent pregnancy were 6.9% (12 studies) after second-stage cesarean delivery and 2.6% (8 studies) after operative vaginal delivery. A total of 7 studies encompassing 75,460 patients compared the primary outcome of spontaneous preterm birth after second-stage cesarean delivery vs operative vaginal delivery in an index pregnancy with an odds ratio of 2.01 (95% confidence interval, 1.57-2.58) in favor of operative vaginal delivery. However, most studies did not include important confounding factors, did not address exposure misclassification because of failed operative vaginal delivery, and considered operative vaginal delivery as a homogeneous category with no distinction between forceps- and vacuum-assisted deliveries.

CONCLUSION

Although a synthesis of the existing literature suggests that the risk of spontaneous preterm birth is higher in those with a previous second-stage cesarean delivery than in those with operative vaginal delivery, the risk of bias in these studies is very high. Findings should be interpreted with caution.

Emergency caesareans are associated with an increased risk of recurrent early preterm birth: a commentary

This article includes Author Insights, a video abstract available at: https://vimeo.com/733549553.

Planned cesarean delivery vs planned vaginal delivery: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

There are over 145 million births worldwide, with over 30 million cesarean deliveries yearly. There are limited data comparing the perinatal and maternal outcomes between planned cesarean delivery and planned vaginal delivery. This study aimed to evaluate perinatal and maternal morbidity and mortality by meta-analysis of randomized controlled trials that randomly assigned patients to either planned cesarean delivery or planned vaginal delivery.

DATA SOURCES

Scopus, PubMed, CINAHL, Cochrane Library, and the World Health Organization clinical trial databases were searched from inception through August 2022.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials that compared planned cesarean delivery with planned vaginal delivery at any gestational age and for any delivery indication were included.

METHODS

Two authors independently extracted data. PRISMA guidelines were used for data extraction and quality assessment. The primary outcome was perinatal mortality. The summary measures were reported as relative risks or as mean differences with 95% confidence intervals. Pooled odds ratios and 95% confidence intervals were calculated using Mantel-Haenszel random-effects models for outcomes.

RESULTS

In 15 primary randomized controlled trials, 3265 patients were randomized to planned cesarean delivery and 3353 to planned vaginal delivery. The incidence of perinatal deaths was not different (1.3% vs 1.3%; relative risk, 0.71; 95% confidence interval, 0.33-1.52). Planned cesarean delivery was associated with lower neonatal incidences of low umbilical artery pH (0.3% vs 2.4%; relative risk, 0.18; 95% confidence interval, 0.05-0.67), birth trauma (0.3% vs 0.7%; relative risk, 0.46; 95% confidence interval, 0.22-0.96), tube feeding requirement (2.5% vs 7.1%; relative risk, 0.36; 95% confidence interval, 0.19-0.66), and hypotonia (0.4% vs 3.5%; relative risk, 0.11; 95% confidence interval, 0.03-0.47), compared to planned vaginal delivery. Chorioamnionitis was less frequent in the planned cesarean delivery group (0.3% vs 1.0%; relative risk, 0.27; 95% confidence interval, 0.08-0.98). Wound infection was more common in the planned cesarean delivery group (1.9% vs 1.1%; relative risk, 1.61; 95% confidence interval, 1.04-2.52). Lower rates were observed in the planned cesarean delivery group for urinary incontinence at both ≤3 months (8.7% vs 12.2%; relative risk, 0.71; 95% confidence interval, 0.59-0.85) and 1 to 2 years (16.9% vs 22%; relative risk, 0.77; 95% confidence interval, 0.67-0.88) and for a painful perineum at 2 years (4% vs 6.2%; relative risk, 0.64; 95% confidence interval, 0.47-0.87) compared to planned vaginal delivery. Among singleton pregnancies, planned cesarean delivery was associated with a lower rate of perinatal death (0.69% vs 1.81%; relative risk, 0.45; 95% confident interval, 0.21-0.93).

CONCLUSION

Planned cesarean delivery and planned vaginal delivery were associated with similar rates of perinatal and maternal mortality in this meta-analysis of randomized controlled trials. Planned cesarean delivery was associated with significant decreases in adverse neonatal outcomes such as low umbilical artery pH, birth trauma, tube feeding requirement, and hypotonia, and significant decreases in chorioamnionitis, urinary incontinence, and painful perineum. Planned vaginal delivery was associated with significant decreases in need for general anesthesia and wound infection. Further randomized trials are needed to assess the risks and benefits of planned cesarean delivery vs planned vaginal delivery in lower-risk patients and in the general population.

Association between interpregnancy interval and maternal and neonatal adverse outcomes in women with a cesarean delivery: a population-based study

BACKGROUND

Interpregnancy interval (IPI) has been linked with several maternal and neonatal adverse events in the general population. However, the association between IPI and maternal and neonatal outcomes in women whose first delivery was by cesarean delivery is unclear. We aimed to investigate the association between IPI after cesarean delivery and the risk of maternal and neonatal adverse events.

METHODS

Women (aged ≥ 18 years) whose first delivery was cesarean delivery with 2 consecutive singleton pregnancies from the National Vital Statistics System (NVSS) database between 2017 and 2019 were included in this retrospective cohort study. In this post-hoc analysis, logistic regression analyses were used to examine IPI (≤ 11, 12-17, 18-23 [reference], 24-35, 36-59, and ≥ 60 months) in relation to the risk of repeat cesarean delivery, maternal adverse events (maternal transfusion, ruptured uterus, unplanned hysterectomy, and admission to an intensive care unit), and neonatal adverse events (low birthweight, premature birth, Apgar score at 5 min < 7, and abnormal conditions of the newborn). Stratified analysis based on age (< 35 and ≥ 35 years) and previous preterm birth.

RESULTS

We included 792,094 maternities, 704,244 (88.91%) of which underwent a repeat cesarean delivery, 5,246 (0.66%) women had adverse events, and 144,423 (18.23%) neonates had adverse events. After adjusting for confounders, compared to an IPI of 18-23 months, the IPI of ≤ 11 months [odds ratio (OR) = 1.55, 95% confidence interval (CI): 1.44-1.66], 12-17 months (OR = 1.38, 95%CI: 1.33-1.43), 36-59 months (OR = 1.12, 95%CI: 1.10-1.15), and ≥ 60 months (OR = 1.19, 95%CI: 1.16-1.22) were associated with an increased risk of repeat cesarean delivery. In terms of maternal adverse events, only IPI of ≥ 60 months (OR = 0.85, 95%CI: 0.76-0.95) was observed to be associated with decreased risk of maternal adverse events in women aged < 35 years. In analysis of neonatal adverse events, IPI of ≤ 11 months (OR = 1.14, 95%CI: 1.07-1.21), 12-17 months (OR = 1.07, 95%CI: 1.03-1.10), and ≥ 60 months (OR = 1.05, 95%CI: 1.02-1.08) were related to an increased risk of neonatal adverse events.

CONCLUSION

Both short and long IPI were associated with an increased risk of repeat cesarean delivery and neonatal adverse events, and women < 35 years may benefit from a longer IPI.