Key messages

Findings from studies that included women without a previous caesarean section and studies that included a mix of women with or without a previous caesarean section (where most had no previous caesarean section):

• It is unclear whether any of the induction of labour methods worked better than inserting a low-dose (≤ 50 μg) of misoprostol into the vagina in achieving vaginal delivery within 24 hours, reducing the risk of caesarean section due to concerns about the baby's well-being, and preventing the death of the baby.

• Nitric oxide donors, osmotic cervical dilators, balloon catheters, and taking a low-dose (≤ 50 μg) of misoprostol by mouth probably help reduce the risk of excessive uterine contractions that can distress the baby compared to low-dose (≤ 50 μg) vaginal insertion of misoprostol.

• Future research is needed to improve our confidence in the evidence.

What is induction of labour?

Induction of labour is the process of starting labour using medical methods, which is often needed if a pregnancy goes beyond the due date or if there are concerns about the health of the mother or baby. There are five types of labour induction methods, described below.

• Medication-based methods (hormonal medications like misoprostol, dinoprostone, and oxytocin are given vaginally, orally (through the mouth), or intravenously (into a vein))

• Mechanical methods (typically a balloon catheter is inserted vaginally to dilate (open) the cervix)

• Surgical methods (known as amniotomy, this involves intentionally rupturing the membrane ('breaking the water'))

• Combination methods (using both medication and mechanical or surgical techniques to improve effectiveness)

• Alternative methods (such as acupuncture and herbal supplements).

What did we want to find out?

We wanted to know the most effective and safest labour induction method for pregnant women at or after 37 weeks with a live baby.

What did we do?

We searched for studies comparing labour induction methods in women at or beyond 37 weeks of pregnancy. We looked at methods recommended in international labour induction guidelines and in previous Cochrane reviews. We compared and summarised the results of the studies and rated our confidence in the evidence based on factors such as study methods and sizes.

What did we find?

We reviewed 106 studies involving 30,348 women from 35 countries, assessing 13 labour induction methods and one control intervention (no routine labour induction method or a policy of waiting (expectant management)).

The studies included the following groups of women.

• Most studies focused on women without a previous caesarean section.

• Two studies specifically included only women with a previous caesarean section.

• Seven studies included a mix of women (with and without a previous caesarean section, where most had no previous caesarean section)

  • Three studies clearly reported that they included a mix of women.

  • Four studies did not report this information; however, because more than half of women were first-time mothers, we assumed that these studies also included a mix of women with most having no previous caesarean section.

We assessed the following methods.

• Eight medication-based methods: low-dose (≤ 50 μg) misoprostol given via oral, vaginal, or sublingual/buccal (inside the mouth) routes; controlled-release misoprostol vaginal pessary (tampon-like device); dinoprostone (vaginal gel/tablet or controlled-release vaginal pessary); oxytocin; and nitric oxide donors

• Two mechanical methods: balloon catheters and osmotic cervical dilators

• Three combination methods: oxytocin with amniotomy; balloon catheter with oxytocin; and balloon catheter with low-dose (≤ 50 μg) misoprostol

The following findings summarise the results for our four key outcomes among women without a previous caesarean section and a mix of women with or without a previous caesarean section: failure to give birth vaginally within 24 hours, caesarean section due to concerns about the baby's well-being, uterine contractions that can distress the baby, and death of the baby.

• There was no clear evidence that any method is more effective than low-dose (≤ 50 μg) vaginal insertion of misoprostol for such key outcomes as failure to give birth vaginally within 24 hours, caesarean section due to concerns about the baby's well-being, and death of the baby.

• When compared with low-dose (≤ 50 μg) vaginal insertion of misoprostol, nitric oxide donors, osmotic dilators, balloon catheters, and low-dose (≤ 50 μg) oral ingestion of misoprostol probably reduce the risk of excessive uterine contractions that can distress the baby.

There is not enough evidence to indicate the safest and most effective labour induction method for women with previous caesarean section.

What are the limitations of the evidence?

We have mostly moderate to little confidence in the evidence. Our confidence was reduced due to problems with the study methods and because there were not enough studies to be certain about the results. Many studies did not collect or report serious unwanted effects for women and babies such as death of the baby and excessive uterine contractions that can distress the baby. Lastly, the studies did not look at all methods of inducing labour that we were interested in for our planned outcomes.

How up-to-date is this evidence?

The evidence is current to 1 February 2023.