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Maternal or fetal complications, following the insertion of a balloon catheter to induce labour, are rare. Pain or discomfort was most common affecting around 1 in 400 women. Balloon displacement, bleeding or abnormal fetal heart rate affected less than 1 in 1,000.

The catheter is a device inserted through the cervix, where inflated balloons on the end of a tube 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.

Individual trials have indicated that catheter induction could be a safer alternative. This review is the first to gather the available evidence from 26 studies including 8,292 women that have reported the adverse event rate for catheters.

It supports balloon catheters as an induction method for low-risk pregnancies that could allow women to stay at home, benefiting the mother and saving NHS resources.

Why was this study needed?

NHS maternity data for England showed that 29.4% of women had induced labour in 2016-17, a rise from 20.3% a decade previously.

Prostaglandin E2 drugs, given in the form of vaginal tablets, gels or pessaries, are the currently recommended method. Prostaglandins encourage the cervix to soften and shorten (known as ripening) and make the uterus contract. Sometimes they cause it to contract too much, which can affect the baby or in severe cases damage the womb, especially in mothers who have had a previous caesarean section. Induction happens in hospital because women need monitoring for complications.

Prior studies show that balloon catheters are equally effective but less likely to overstimulate the uterus. This could allow women to be induced at home, improving the birth experience.

Therefore, it is important to know that balloon catheters are safe from the time of insertion to removal or expulsion, even when the mother is not monitored.

What did this study do?

This systematic review included 26 studies (21 randomised controlled trials, five cohort studies) involving 8,292 women receiving balloon catheter induction for a single, live, head-down baby. It looked specifically at the safety of balloons but did not assess their effectiveness at ripening the cervix compared to prostaglandins.

Eligible studies had to include over 400 women and report adverse effects for the period the catheter was in place (including stating if there were none). Study authors of all potentially relevant studies were contacted to obtain this information. This led to the exclusion of 18 studies were authors could not be contacted.

Studies using other drugs or mechanical induction methods alongside were also excluded, including those where catheters were used as a second-option after failed induction.

Twenty-three studies took place in hospital, two in outpatient settings. The majority (22) reported use of single balloon catheters. Balloon volume varied from 30 to 80ml.

Quality of included studies was assessed to be good. Most inductions were said to be for post-term pregnancy, though limited information on maternal characteristics was available. The women are likely to be from selected low-risk groups, given that the studies are mainly trials. Study designs were trials and cohort studies, and there was no standard set of complications measured.

What did it find?

  • Pain or discomfort was the most common adverse effect reported by 0.26% of women (95% confidence interval [CI] 0.00 to 1.01%). This outcome was reviewed by 17 studies including 5,754 women, with 31 pain instances reported in six studies. In most cases, induction continued normally.
  • Vaginal bleeding affected 0.07% (95% CI 0.00 to 0.33%) as reported by 18 out of 6,566 women (in 10 of 18 studies). Four cases resulted in caesarean section, in others, either catheter induction continued, or an alternative method was pursued.
  • Balloon displacement occurred in 0.07% (95% CI 0.00 to 0.62%) with 12 instances reported for 12 out of 2,397 women (four of 10 studies). This required an alternative induction method in most cases. Uncomplicated balloon rupture was reported for only one of 3,222 women (12 studies).
  • Unintentional rupture of the membranes occurred in 0.04% (95% CI 0.00 to 0.69%) (19 out of 2,989 women across 12 studies). No infections were reported as a result. Uterine overstimulation was reported for only one of 4,812 women (20 studies), while one of 3,707 women (14 studies) was reported to have excessively prolonged contractions (uterine hypertonus).
  • Non-reassuring fetal heart rate occurred at a rate of 0.01% (95% 0.00 to 0.22%) with 15 instances among 5,351 women (five of 17 studies). Only two of these babies had poor health at birth (low Apgar score) and spent a brief period in intensive care. One of 4,318 women (11 studies) reported decreased fetal movements, but labour and delivery continued without complication. Altered fetal position after catheter insertion was reported for four of 6,046 women (16 studies).

What does current guidance say on this issue?

The NICE 2008 guideline on 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).This guideline advises against the routine use of mechanical procedures such as balloon catheters, due to limited evidence at the time. These recommendations are, though, in the process of update.

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 group.

What are the implications?

The very low complication rate indicates that balloon catheter induction could take place with minimal monitoring. This could potentially make a large difference to maternity services. Healthy and low-risk women could be allowed to return home following catheter placement. This could be more comfortable for women while saving bed space and NHS costs.

A drawback is the limited evidence available for double balloon catheters, the device recommended by NICE. The adverse event rate among women receiving the comparison arm (e.g. prostaglandin E2) could be helpful for direct comparison.

It is also difficult to know which women, for example, those with risk factors, may be unsuitable for catheter induction, though some of these studies included women with previous caesarean.

Citation and Funding

Diederen M, Gommers J, Wilkinson C, et al. Safety of the balloon catheter for cervical ripening in outpatient care: complications during the period from insertion to expulsion of a balloon catheter in the process of labour induction: a systematic review. BJOG. 2017. [Epub ahead of print].

No funding was involved in the development of this systematic review.



NHS Digital. NHS Maternity Statistics 2016-17. Leeds: NHS Digital; 2017.

NICE. Inducing labour. CG70. London: National Institute for Health and Care Excellence; 2008.

NICE. Induction of labour. Evidence update July 2013. A summary of selected new evidence relevant to NICE clinical guideline 70 ‘Induction of labour’ (2008). Evidence Update 44. London: National Institute for Health and Care Excellence; 2013.

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.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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