Induced labour

Synthetic versions of the natural hormone produced by your body have been designed to prepare or ‘ripen’ the cervix for labour but they can also sometimes start labour. They can be administered as a gel or pessary that is inserted into your vagina during a vaginal examination. A pessary slowly releases the prostaglandin over 12–24 hours and the gel is usually given every 6-8 hours. Several doses may be required to induce labour. Once the prostaglandin is in place, you will be advised to lie down and rest for at least 30 minutes and your baby’s heart rate will be monitored during this time. The advantages are that inducing labour with prostaglandins may mimic normal labour and allow you to resume active birthing once the period of monitoring indicates all is well. Sometimes prostaglandins can cause side-effects such as nausea, vomiting or diarrhoea, local allergic reactions and occasionally they can cause the uterus to over contract (tonic or hypertonic contractions), with little rest in between. Overstimulation of the uterus may reduce oxygenation to the baby and cause its heart rate to slow. If this occurs you will be asked to lie on your left side and the prostaglandin may need to be removed or you may be given another medication to relax the uterus. You should inform your midwife immediately if you experience any of the following:

If the prostaglandins have not started labour, it is usual to require additional methods of induction or to wait and try again at a later date, depending on your particular circumstances.

ARM and a Syntocinon infusion are often required after the prostaglandins have ‘ripened’ the cervix for labour. If you have had previous pregnancies or your cervix is already soft and partially open, your obstetrician may decide to induce your labour using ARM and/or Syntocinon rather than commencing with the prostaglandins. Your obstetrician will likely use a small plastic hook-like instrument (called an amnihook) that is inserted through your vagina during a vaginal examination. It makes a small hole in the membranes in front of the baby’s head to release the amniotic fluid (forewaters) inside. This allows the baby’s head to press down on the cervix and releases natural prostaglandins around the cervix causing contractions. Sometimes the ARM is enough to initiate labour but most women will also require a Syntocinon infusion to start the contractions.

Natural oxytocin is a hormone produced by the pituitary gland in the brain. This hormone is responsible for producing uterine contractions and the ‘let-down’ reflex during breast feeding. The synthetic version called Syntocinon is used to start the uterus contracting and usually works best once the membranes have been ruptured. Syntocinon is given via an IV infusion in carefully measured amounts over several hours. The baby will need to be monitored continuously during this time with the CTG so your midwife and obstetrician can see yours (contractions) and your baby’s response (heart rate) to the induction. As with the prostaglandins, Syntocinon may cause the uterus to over contract and cause the baby’s heart rate to slow or quicken beyond the normal range (110-160 beats per minute), in which case the infusion will be stopped and you may be given a medication to relax the uterus and be asked to lie on your left side.

Induction of labour has benefits and risks that must be carefully considered during your informed consent discussion with your obstetrician. The benefits are that induction of labour and birth is safer for babies than allowing the pregnancy to go past term and the wellbeing of mothers who have existing or pregnancy-related conditions will likely improve with the birth (e.g. pre-eclampsia). The general risks of induction of labour are that it may be may be less efficient and more painful than normal spontaneous labour, leading to a greater need for epidural anaesthesia and assisted or instrumental birthing methods; particularly if this is your first pregnancy. If an induction of labour fails, the available options are:

Induction of labour is contraindicated in circumstances where the risks of doing so outweigh the risks of waiting a little longer or where caesarean birth is considered safer or more appropriate. Some of these reasons include: the placenta or cord lie in front of the baby, the mother’s pelvis is too small, the mother has previously had major surgery to her uterus (not lower uterine segment caesarean section), the baby is lying in an unfavourable position for birth (e.g. the baby is lying across the mother’s abdomen rather than head-down), the baby has a heart rate pattern outside the normal range on the CTG, or the mother has active genital herpes.