Induction methods for women who have had a prior caesarean birth

What is the issue?

Labour induction is a common procedure, carried out when it is judged to be safer for a baby to be born than to continue a pregnancy. When a woman who has had a caesarean in the past gives birth, current clinical practice supports helping her to have a vaginal birth. However, there is a higher risk of complications from induction for women who have previously had a caesarean section.

Methods for induction include: prostaglandin medication (including oral or vaginal prostaglandins E2 (PGE2) or misoprostol); mifepristone; mechanical methods (including Foley catheters and double-balloon catheters); nitric oxide donors (such as isosorbide mononitrate); and oxytocin. This review looked at the harms and benefits of different methods for induction of labour in women with a prior caesarean birth, if induction of labour was required in their current pregnancy.

Why is this important?

Lots of women have caesareans: across the world between one in four and one in two babies are born by caesarean section. Many women go on to have another pregnancy, and we want to know how to deliver these babies safely. Women with a prior caesarean birth have an increased risk of uterine scar rupture, particularly when labour is induced. This is a serious complication, often leading to negative outcomes for mother and child, such as hysterectomy, genitourinary tract injury, and postpartum blood transfusions for the mother, and neurological impairment or even death for the child.

What evidence did we find?

We searched for studies on 31 August 2016. Eight small randomised controlled trials are included in this updated review, with data from 707 women and babies. The studies compared different methods of inducing labour, so results could not be combined.

There were design problems in all of the trials: women and health professionals knew which induction method was being used in seven out of eight trials, which may have affected clinical decisions. Women were left out of the analysis in some trials, and trials often did not report important outcomes (vaginal birth not achieved within 24 hours of induction, overstimulation of the uterus with changes to the baby's heart rate, caesarean section, serious illness or death of the baby, serious illness or death of the mother).

The trials were too small to show clear differences. The quality of the evidence was very low, low, or moderate, because the trials were small and had high risk of bias. We cannot be certain about the results, and future research may show something different.

What does this mean?

There is not enough information available from randomised controlled trials to advise on the best methods of labour induction in women with a previous caesarean birth. More high-quality randomised controlled trials are needed to find out which method is best for mothers and babies. However, such trials are unlikely to be carried out because they would need a very large number of participants in order to study the risk of infrequent but serious outcomes (such as rupture of the woman's uterus). Other types of studies (i.e. non-randomised controlled trials) might be the best alternative. Future research could focus on those methods of induction that are believed to be effective and have a low risk of serious harm. The outcomes identified as important in this review could be utilised in future studies.

Authors' conclusions: 

RCT evidence on methods of induction of labour for women with a prior caesarean section is inadequate, and studies are underpowered to detect clinically relevant differences for many outcomes. Several studies reported few of our prespecified outcomes and reporting of infant outcomes was especially scarce. The GRADE level for quality of evidence was moderate to very low, due to imprecision and study design limitations.

High-quality, adequately-powered RCTs would be the best approach to determine the optimal method for induction of labour in women with a prior caesarean birth. However, such trials are unlikely to be undertaken due to the very large numbers needed to investigate the risk of infrequent but serious adverse outcomes (e.g. uterine rupture). Observational studies (cohort studies), including different methods of cervical ripening, may be the best alternative. Studies could compare methods believed to provide effective induction of labour with low risk of serious harm, and report the outcomes listed in this review.

Read the full abstract...
Background: 

Women with a prior caesarean delivery have an increased risk of uterine rupture and for women subsequently requiring induction of labour it is unclear which method is preferable to avoid adverse outcomes. This is an update of a review that was published in 2013.

Objectives: 

To assess the benefits and harms associated with different methods used to induce labour in women who have had a previous caesarean birth.

Search strategy: 

We searched Cochrane Pregnancy and Childbirth's Trials Register (31 August 2016) and reference lists of retrieved studies.

Selection criteria: 

Randomised controlled trials (RCTs) comparing any method of third trimester cervical ripening or labour induction, with placebo/no treatment or other methods in women with prior caesarean section requiring labour induction in a subsequent pregnancy.

Data collection and analysis: 

Two review authors independently assessed studies for inclusion and trial quality, extracted data, and checked them for accuracy.

Main results: 

Eight studies (data from 707 women and babies) are included in this updated review. Meta-analysis was not possible because studies compared different methods of labour induction. All included studies had at least one design limitation (i.e. lack of blinding, sample attrition, other bias, or reporting bias). One study stopped prematurely due to safety concerns.

Vaginal PGE2 versus intravenous oxytocin (one trial, 42 women): no clear differences for caesarean section (risk ratio (RR) 0.67, 95% confidence interval (CI) 0.22 to 2.03, evidence graded low), serious neonatal morbidity or perinatal death (RR 3.00, 95% CI 0.13 to 69.70, evidence graded low), serious maternal morbidity or death (RR 3.00, 95% CI 0.13 to 69.70, evidence graded low). Also no clear differences between groups for the reported secondary outcomes. The GRADE outcomes vaginal delivery not achieved within 24 hours, and uterine hyperstimulation with fetal heart rate changes were not reported.

Vaginal misoprostol versus intravenous oxytocin (one trial, 38 women): this trial stopped early because one woman who received misoprostol had a uterine rupture (RR 3.67, 95% CI 0.16 to 84.66) and one had uterine dehiscence. No other outcomes (including GRADE outcomes) were reported.

Foley catheter versus intravenous oxytocin (one trial, subgroup of 53 women): no clear difference between groups for vaginal delivery not achieved within 24 hours (RR 1.47, 95% CI 0.89 to 2.44, evidence graded low), uterine hyperstimulation with fetal heart rate changes (RR 3.11, 95% CI 0.13 to 73.09, evidence graded low), and caesarean section (RR 0.93, 95% CI 0.45 to 1.92, evidence graded low). There were also no clear differences between groups for the reported secondary outcomes. The following GRADE outcomes were not reported: serious neonatal morbidity or perinatal death, and serious maternal morbidity or death.

Double-balloon catheter versus vaginal PGE2 (one trial, subgroup of 26 women): no clear difference in caesarean section (RR 0.97, 95% CI 0.41 to 2.32, evidence graded very low). Vaginal delivery not achieved within 24 hours, uterine hyperstimulation with fetal heart rate changes, serious neonatal morbidity or perinatal death, and serious maternal morbidity or death were not reported.

Oral mifepristone versus Foley catheter (one trial, 107 women): no primary/GRADE outcomes were reported. Fewer women induced with mifepristone required oxytocin augmentation (RR 0.54, 95% CI 0.38 to 0.76). There were slightly fewer cases of uterine rupture among women who received mifepristone, however this was not a clear difference between groups (RR 0.29, 95% CI 0.08 to 1.02). No other secondary outcomes were reported.

Vaginal isosorbide mononitrate (IMN) versus Foley catheter (one trial, 80 women): fewer women induced with IMN achieved a vaginal delivery within 24 hours (RR 2.62, 95% CI 1.32 to 5.21, evidence graded low). There was no difference between groups in the number of women who had a caesarean section (RR 1.00, 95% CI 0.39 to 2.59, evidence graded very low). More women induced with IMN required oxytocin augmentation (RR 1.65, 95% CI 1.17 to 2.32). There were no clear differences in the other reported secondary outcomes. The following GRADE outcomes were not reported: uterine hyperstimulation with fetal heart rate changes, serious neonatal morbidity or perinatal death, and serious maternal morbidity or death.

80 mL versus 30 mL Foley catheter (one trial, 154 women): no clear difference between groups for the primary outcomes: vaginal delivery not achieved within 24 hours (RR 1.05, 95% CI 0.91 to 1.20, evidence graded moderate) and caesarean section (RR 1.05, 95% CI 0.89 to 1.24, evidence graded moderate). However, more women induced using a 30 mL Foley catheter required oxytocin augmentation (RR 0.81, 95% CI 0.66 to 0.98). There were no clear differences between groups for other secondary outcomes reported. Several GRADE outcomes were not reported: uterine hyperstimulation with fetal heart rate changes, serious neonatal morbidity or perinatal death, and serious maternal morbidity or death.

Vaginal PGE2 pessary versus vaginal PGE2 tablet (one trial, 200 women): no difference between groups for caesarean section (RR 1.09, 95% CI 0.74 to 1.60, evidence graded very low), or any of the reported secondary outcomes. Several GRADE outcomes were not reported: vaginal delivery not achieved within 24 hours, uterine hyperstimulation with fetal heart rate changes, serious neonatal morbidity or perinatal death, and serious maternal morbidity or death.

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