Nearly a third of mums need inductions to bring their babies into the world. Obstetrician Dr Emma Parry outlines what to expect.
Induction of labour is the process of bringing labour on earlier than it would naturally happen. It is very common and occurs in up to 30% of pregnancies. The decision is not made lightly as it is often associated with an increased likelihood of other interventions such as epidurals, assisted deliveries and caesarean sections. Once a decision for an induction has been made a hospital birth is planned.
There are a range of reasons for an Induction of Labour (IOL) and quite a few methods of achieving it. IOL is close to my heart as my MD (research thesis for doctors) was all about IOL and both my pregnancies ended with an induction.
So what about all those old wives' tales? In the past many substances were used to induce labour. They included castor oil and other medications to increase bowel activity. Essentially, these substances caused diarrhoea. This had a variable effect on the uterus and was not pleasant! I guess the modern variant is a spicy curry. There's no research to back the theory that it works, though.
My mother-in-law was sent on a bus through the bumpy cobbled streets of Docklands in London over 50 years ago in an attempt to get labour started. But it didn't work.
One trick which has some science behind it is to have a "romantic" evening with your partner. Semen contains prostaglandins and so theoretically should promote labour. However, there are no studies on this and many women do not feel keen on the idea at 41 weeks pregnant (and often neither do their partners!).
What leads to an induction?
Most IOLs will happen at or close to term (37 weeks onwards). The top four reasons in most hospitals are: pre-eclampsia, pre-labour rupture of membranes, intra-uterine growth restriction (IUGR) and post-dates pregnancy.
Pre-eclampsia: This is a condition unique to pregnancy. The symptoms are high blood pressure and swelling. There are also usually "leaky" kidneys with protein being found in the urine. Often the pregnancy can be prolonged with medications but ultimately delivery is the only real cure. Complications can occur if the condition is severe. In many cases once the woman reaches term a decision is made to deliver the baby as the outcomes are generally better. This will usually mean an IOL.
Pre-labour rupture of membranes: This is where the membranes rupture (waters break) before contractions start. In most cases the labour will follow on from the rupture but in some cases this is not the case. After a period of time labour is usually induced as there is an increased risk of infection in the womb the longer the membranes are ruptured.
Intra-uterine growth restriction: This is where the baby is not growing well in the womb. Usually it is due to the placenta not functioning as well as it did previously when the demands were lower and the baby was smaller. Delivery is often the best option as this means the baby is no longer reliant on the placenta for nutrition.
Post-dates pregnancy: In the time of our grandmothers some pregnancies would go weeks overdue (yes, up to 44-45 weeks!). In current times most mothers would throw up their hands in horror at the thought of being pregnant for so long. Nowadays IOL is recommended when a pregnancy is overdue - not just to keep mother's sanity but because there is good research to support IOL.
Around 20 years ago it had been noted that pregnancies that went a long way over the due date were at higher risk of a stillbirth. Induction had become a safe option and so some large studies were done comparing IOL with a policy of waiting for labour to start naturally. The findings showed that once a pregnancy reached 42 weeks there is a benefit in using IOL as it reduces the chances of stillbirth. It also showed a reduction in the incidence of caesarean section. This was not expected as IOL is an intervention and generally these increase other interventions. But this is not true when there is a post-dates pregnancy.
Some further research has also looked at the effect of maternal age and it appears that for older mums (over 40) the risks increase at 40 weeks and that an earlier IOL is a good idea.
Other reasons for IOL include bleeding, antibodies in the blood, diabetes and other medical and social conditions. Social? IOL doesn't sound like an excuse for a party. Actually this is the term used when there is no medical reason for an IOL. Examples might include a partner going to sea for six months, having to deliver in another unit etc. In general, health professionals will try to avoid this as IOL is an intervention with a potential increased risk of other interventions.
Methods can be divided into hormonal and mechanical. The cervix (neck of the womb) acts as a strong valve throughout the nine months of pregnancy. Above it the uterus enlarges and gets heavier and in the last month of pregnancy the baby's head presses down on the cervix with Braxton Hicks contractions (practice contractions) adding to the pressure. Throughout all of this the cervix needs to hang on tight to stop the baby coming out too early. In the latent phase of labour (the last few weeks of pregnancy) the cervix changes in shape, texture and at a molecular level. The cervix contains strong fibres supported in a small amount of "glue" called stroma. There is a hormonal change at the end of pregnancy which means water is absorbed into the cervix and the strong fibres are dissolved out and no longer strongly adhere to each other. The cervix becomes soft and compliant. It's a bit like changing from a sticky toffee to a piece of chewed gum. This means it is easy to stretch the cervix and change its shape.
Many types of hormones have been researched for their ability to induce labour but essentially the best ones are prostaglandins. These are placed next to the cervix in the vagina and absorbed from the vagina. Once they are absorbed they cause the changes in water absorption and also lead to contractions in the womb.
Because they go into the vagina and the cervix does not need to be already open, they are usually the first technique used in an induction. Typically, you would be admitted to hospital for an IOL. You will have a foetal heart rate monitor and be monitored by staff. After this a vaginal examination is done and a dose of prostaglandin is inserted in the vagina. This may be a tablet, gel or a pessary with a string that releases a dose over a long period. After this you may go into labour or a further dose or other measures may be required. In a 24-hour period two or three doses of prostaglandin may be given. Usually labour starts or the cervix opens enough for other techniques after two or three doses. In some cases, though, the prostaglandins may not be effective.
An old technique which has been recently resurrected is the balloon. Using a speculum (used during a smear test) a soft plastic tube is inserted into the cervical canal. This is the opening in the cervix which changes from a few millimetres across to 10cm. Where the tip of the tube sits inside the womb just above the cervix, the balloon is filled with water. A second balloon is blown up on the outside of the cervix. This stretches the lower part of the womb and the cervix and leads to a release of hormones. These are actually natural prostaglandins. The balloon is usually left in place for up to 24 hours. Once it is removed it is usually followed by an amniotomy (see below). It is usually comfortable once in position.
This is the procedure where the waters are artificially broken. The foetus is inside the womb floating in amniotic fluid. There are two layers of membranes lining the womb which keep the amniotic fluid inside. It is not painful to break the membranes but it does involve a vaginal examination and the doctor or midwife pushing their fingers through the cervix to be able to touch the membranes and break them with a small hook. This can sometimes be uncomfortable.
An amniotomy cannot be done until the cervix has opened 2-3cm and many women will have prostaglandins before an amniotomy. Once the membranes are broken there is usually a gush of water which often continues until the baby is born. After an amniotomy the woman often goes into labour, but if this doesn't happen there is one more trick.
Artificial syntocinon works in the same way as oxytocin, a hormome released from a small gland in the brain which causes contractions of the womb and the ducts in the breasts. It is released in increasing amounts towards the end of pregnancy and the number of receptors to it in the womb also increase. Stimulating the nipples also causes oxytocin release.
After artificial or pre-labour rupture of the membranes syntocinon may be given intravenously to start contractions. At this stage you will be in a delivery unit as you need to be closely monitored when this drug is being given. In most cases you will be hooked up to a cardiotocograph (CTG) to monitor the baby's heart rate and how often the contractions are.
This is a vaginal examination where the midwife or doctor puts her finger through the cervix if possible and runs it around the lower part of the uterus, separating the membranes from the uterus without breaking them.
Some studies have shown that if women have this done at 38 and 39 weeks, the chances of them needing an induction for post-dates pregnancy is reduced. In my opinion it is well worth having a couple of vaginal examinations to avoid needing an induction.
Previous Caesarean section: Women who have had a previous C-section will have a scar on their wombs, increasing the risk of tearing during an induction using prostaglandins, compared with other methods of induction. However the actual risk is still very low.
In many units if the mum has had a previous C-section, staff will prefer to use a balloon to open the cervix to allow an amniotomy rather than prostaglandins.
Pre-labour rupture of membranes: In this case both syntocinon and prostaglandins can be used to induce labour. The prostaglandins are often perceived as gentler but there may be an increased risk of developing infection during labour and after birth. It will really depend on the individual circumstances.
In hospital or at home?
An induction is usually performed in hospital and if this happens to you, you will stay in until you deliver the baby. This can take a few days.
There is emerging research and practice change that may mean an induction can be performed with the mum going home between examinations. This is likely to be restricted to those inductions where the indication is post-dates pregnancy or social. The labour and birth would still be in hospital.
Dr Emma Parry is a specialist obstetrician and gynaecologist, a sub-specialist in Maternal-Foetal Medicine, Clinical Director of MFM at Auckland Hospital and a spokesperson for the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG). She's involved in training and teaching for both medical and midwifery colleagues and has used her skills in Bhutan in the Himalayas, where she helped establish a high-risk maternity service.