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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Double-balloon catheters seem to be as effective as vaginal prostaglandin drugs for inducing labour, while also avoiding overstimulation of the womb.
The catheter is a device inserted through the cervix, where inflated balloons put pressure on the cervix helping it to “ripen” and start contractions. Prostaglandin drugs are the current recommended induction method, but uterine (womb) overstimulation, where contractions become too frequent or long, is a recognised side effect.
This trial found that with either method half of women went on to a vaginal delivery within 24 hours and avoided the need for a caesarean section. About a quarter of women in either group eventually had a caesarean section. However, the double-balloon catheter reduced the risk of uterine overstimulation.
Recent NICE guidance states there is adequate evidence on the safety and effectiveness of double-balloon catheter in women who have not had a previous caesarean. These findings support this option, but treatment satisfaction and use in women with different maternity history or reasons for induction are important considerations that still need exploring.
Why was this study needed?
Around 1 in 5 women have their labour started artificially (induced). Women are offered induction if their baby is overdue, or there are other reasons why continuing the pregnancy poses a risk to mother or baby. Induced labour can increase the need for pain-relief and assisted delivery.
Current guidance recommends the use of prostaglandin E2 drugs, given in the form of vaginal tablets, gels or pessaries. Prostaglandins encourage the cervix to soften and shorten (known as ripening) and make the uterus contract. Sometimes they can cause it to contract too much (overstimulation) which can affect the baby or in severe cases cause damage to the womb (especially in mothers who have had a previous caesarean section).
Inserting a double-balloon catheter, a hollow tube, is an alternative mechanical procedure. The catheter passes through the cervix into the uterus. Two balloons put pressure on the cervix and cause release of natural prostaglandins, both of which ripen the cervix and encourage contractions.
This review adds to the evidence on the safety and applicability of this procedure.
What did this study do?
This systematic review and meta-analysis identified nine randomised controlled trials including 1866 women assigned to prostaglandin E2 or to double-balloon catheters.
Studies included women whose waters had not yet broken, who were expecting a single baby, positioned head down and with reassuring heart rate. Main outcomes were rates of vaginal delivery within 24 hours and the proportion of women needing a caesarean.
The studies were of high quality but varied considerably in participant characteristics, prostaglandin E2 preparation and dosing, catheter volume, induction protocols and outcome definitions. Although the review therefore reflects practice better, it can make it harder to compare studies and be confident of their combined results. Subgroup analyses taking account of these differences did not alter the findings. No studies were UK-based.
What did it find?
- The proportion of women achieving vaginal delivery within 24 hours was similar between groups – 55 of 100 women in the catheter group and 53 of 100 in the prostaglandin group (risk ratio [RR] 0.95, 95% confidence interval [CI] 0.78 to 1.16, seven studies). However, the results of the individual studies differed significantly from each other (heterogeneity), which reduces confidence in this finding.
- Likelihood of caesarean section was also comparable and needed by 28 of 100 women in the catheter group compared with 26 of 100 (RR 0.92, 95% CI 0.79 to 1.07, nine studies).
- Prostaglandin E2 was associated with significantly increased risk of uterine overstimulation (RR 10.02, 95% CI 3.99 to 25.17, five studies), which occurred in about 11 of 100 in the drug group compared to less than one in 100 who received the balloon catheter. The wide confidence interval suggests caution in interpreting these findings. Those receiving prostaglandin E2 were also more likely to have their baby admitted to neonatal intensive care, though this result only just reaches statistical significance (RR 1.31, 95% CI 1.01 to 1.69, four studies).
What does current guidance say on this issue?
The NICE 2008 guideline Inducing labour recommends vaginal prostaglandin E2 as the preferred method, unless there are specific reasons for not using it (in particular the risk of uterine overstimulation). Dinoprostone is the drug licensed for this use in the UK, given as a gel, tablet or pessary. When offering prostaglandin E2, healthcare professionals should inform women about the risks of uterine overstimulation.
This guideline advises against the routine use of mechanical procedures such as balloon catheters, due to limited evidence at the time. The 2015 interventional procedures guidance on insertion of a double balloon catheter for induction of labour in pregnant women without previous caesarean section concluded that there was adequate evidence to support the use of this procedure for this patient group.
What are the implications?
Double balloon catheters appear to be a safe alternative to prostaglandin E2, in particular for reducing the chance of uterine overstimulation in those at risk. Future research would benefit from focusing on women’s preferences as well as specific populations, such as maternity history, reason for induction, and use of additional drugs or procedures like sweep of membranes.
It remains to be seen whether NICE will update their clinical guideline to recommend the use of balloon catheters in light of the growing evidence supporting their use.
Citation and Funding
Du YM, Zhu LY, Cui LN, et al. Double-balloon catheter versus prostaglandin E2 for cervical ripening and labour induction: a systematic review and meta-analysis of randomised controlled trials. BJOG. 2016.
No financial support was received for this paper.
Bibliography
NHS Choices. Inducing labour. London: Department of Health; 2015.
NICE. Inducing labour. CG70. London: National Institute for Health and Care Excellence; 2008.
NICE. Insertion of a double balloon catheter for induction of labour in pregnant women without previous caesarean section. IPG528. London: National Institute for Health and Care Excellence; 2015.
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