Induction of labour: the different types of induction and the risks and benefits

Following on from the article ‘Induction of labour: what is induction and when to induce’, this article addresses the different types of induction of labour and the risks and benefits of this intervention, with the aim being to provide information to empower women to weigh up their options and make choices about their care. It should be noted that induction of labour is a medical procedure, and the options should be considered with the healthcare provider.

Induction of labour (IOL) refers to the process of artificially starting labour before it begins naturally. In the UK, induction is offered when continuing the pregnancy is thought to pose greater risks than giving birth, such as prolonged pregnancy, or when there are concerns about the baby’s growth or well-being, or concerns about the mother’s well-being, with pre eclampsia and diabetes being conditions of relevance.

The method chosen depends on the woman’s individual circumstances, the condition of the cervix, and local NHS guidelines. Information about the different methods used, and some of the associated risks of each method are outlined below.

Membrane sweep

A membrane sweep is often the first step offered before formal induction. It is performed during a vaginal examination, usually from around 39–41 weeks of pregnancy. The midwife or doctor sweeps a finger around the cervix to separate the membranes from the cervix, encouraging the release of natural prostaglandins. This may start labour on its own and can reduce the need for further induction methods.

While generally safe, it can be uncomfortable and may cause some cramping, bleeding, or irregular contractions. Occasionally, it may lead to the rupture of membranes and trigger contractions that do not progress to established labour, which can be physically and emotionally tiring. Infection risk is very low, but not zero.

Prostaglandins (cervical ripening)

If the cervix is not yet ready (that is, because it is long, firm, and closed), prostaglandins are commonly used to soften and open it, a process known as cervical ripening. In the UK, prostaglandins may be given as a vaginal pessary, gel, or oral tablets, depending on local practice.

The woman should be monitored during this process to ensure contractions are not too strong or frequent and that the baby remains well. Prostaglandins can cause uterine hyperstimulation where the contractions become too strong or too frequent. This may reduce oxygen supply to the baby and lead to abnormal fetal heart rate patterns, sometimes requiring urgent intervention.

Other side effects include nausea, vomiting, diarrhoea, fever, and vaginal discomfort. Rarely, hyperstimulation can contribute to uterine rupture, particularly in women with previous uterine surgery, which is why prostaglandins are often avoided in women who have had a previous caesarean section.

Mechanical methods

Mechanical methods offer an alternative to medication and are used in NHS practice. These involve placing a small balloon catheter, such as a Foley catheter or a Cook balloon, into the cervix. The balloon is gradually inflated, applying pressure to encourage the cervix to open and release natural prostaglandins.

Mechanical methods are less likely to cause excessive contractions (uterine hyperstimulation) and may be suitable for women who cannot use prostaglandins, such as those who have had a previous caesarean birth. They are sometimes used as part of outpatient induction, allowing women to return home while the cervix ripens.

However, insertion can be uncomfortable and may cause vaginal bleeding, cramping, or infection. In rare cases, the catheter may be difficult to insert, or may fall out before effective cervical ripening occurs, meaning additional induction methods are needed.

Artificial rupture of membranes (amniotomy)

Once the cervix has opened sufficiently, labour may be induced by breaking the waters, known as an amniotomy. This is done during a vaginal examination using a small instrument. Breaking the waters can stimulate the release of hormones that encourage contractions, but it is usually only effective when the cervix is already favourable.

Breaking the waters carries a risk of infection, particularly if there is a long gap between membrane rupture and birth. Once the waters are broken, labour is more time limited, and further intervention (such as a Syntocinon drip) is often required if labour does not progress. There is also a small risk of umbilical cord prolapse, where the cord slips down in front of the baby, which is a medical emergency. This risk is higher if the baby’s head is not well engaged in the pelvis.

Oxytocin (Syntocinon) drip

If contractions do not start or strengthen after amniotomy, a synthetic form of oxytocin, called Syntocinon, may be given through an intravenous drip. This stimulates regular contractions and the mother should be closely monitored due to the risk of overly strong contractions. Continuous fetal monitoring is standard during Syntocinon induction.

Syntocinon stimulation is associated with a higher risk of strong, frequent contractions, which can lead to fetal distress. Because continuous fetal monitoring is required, this may limit movement during labour. Women often report more intense pain compared with spontaneous labour, increasing the likelihood of epidural use. Very rarely, excessive contractions can contribute to uterine rupture or postpartum haemorrhage.

General risks, monitoring and choice

Induction of labour is a common and well-established practice – being a valuable and, potentially, life-saving intervention when used appropriately – but it is associated with a higher likelihood of needing further interventions, such as instrumental birth (forceps or ventouse) or caesarean section, particularly in first time mothers. Labour may be longer, more painful, and more medicalised compared with spontaneous labour.

Throughout induction, the baby’s heart rate and the mother’s wellbeing should be monitored.

Women should be involved in decisions about induction, with personalised discussions covering the benefits, risks, and alternatives so that they can give their informed consent to such intervention.

If you have experienced issues in relation to induction of labour and would like to discuss this further with us, please do not hesitate to contact our specialist maternal care team.