The term “Induction of labour” (or IOL for short) means medically intervening to start your labour before natural labour begins. Generally we induce labour when we consider the risk to the mother and / or the baby to be less with IOL than with waiting for spontaneous labour to occur. That said some women choose to have their labour induced because of the significant discomfort that goes with late pregnancy and rarely women have their labours induced for social reasons (ever wondered why those footy players’ wives miraculously give birth a few days before the Grand Final?).

Of course being a medical procedure, IOL carries some – admittedly rare – risks and the process can be unpleasant or unduly painful (not, I might say, that spontaneous labour is always a basket of fruit).

Common reasons for IOL

In this section I will not discuss the scientific research surrounding each reason for IOL because to do so would turn this sheet into something the length of “War and Peace” (and that would mean I would never finish it). For example you could read my information sheet on diabetes in pregnancy to find out why we induce labour in women with diabetes.

The most common (and generally medically accepted) reasons for induction of labour are:

  • Post dates pregnancy. We usually recommend IOL somewhere between 41 and 42 weeks gestation (i.e. between seven and 14 days after your due date) if you have not laboured spontaneously by then.
    Labour is induced for postdates pregnancy because of the small increased risk of a stillbirth occurring or your baby developing severe fetal distress in labour once you have gone over 41 weeks. The exact gestation we induce you at depends upon a number of factors including your preferences, your health and that of your baby and whether or not I have the next weekend off (just kidding!)
  • High blood pressure in pregnancy or preeclampsia.
    With high blood pressure in pregnancy there are a number of bad things that can happen to either the mother or the baby – and these risks are most significant with preeclampsia – with continuation of the pregnancy.
  • Ruptured membranes (broken waters) without labour occurring. Approximately 75% of women whose waters break prior to labour at term go into labour spontaneously within 24 hours of the waters breaking. This means of course that 25% will not go into labour within 24 hours of their waters breaking and sometimes a woman may wait a number of days before she labours spontaneously. Accordingly we usually offer a woman IOL somewhere around 24 hours after her waters have broken if she does not labour spontaneously in the interim.

    We induce labour once the waters have been broken for 24 hours or so because of the small risk of infection causing harm to the baby. Once the waters have broken the protective bag around the baby is no longer able to stop bacteria ascending from the vagina into the uterus.

  • Evidence of fetal compromise. Sometimes placentas simply don’t feed unborn babies as well as they should. If the placenta is not passing an appropriate amount of nutrition across to the baby the baby can grow poorly inside the uterus (we call this Intrauterine Growth Restriction, or IUGR). Now the poor passage of nutrition is not necessarily a problem for babies however placentas that transmit food poorly can sometimes – admittedly rarely – pass oxygen across to the baby poorly with significant adverse consequences.
  • Poor placental function usually manifests as an IUGR baby, diagnosed clinically and confirmed by ultrasound. Other signs of poor placental function are vaginal bleeding in late pregnancy and a low amniotic fluid volume. In all of these instances – particularly when you are full term – we induce labour because of the risk of a stillbirth occurring or your baby being unable to tolerate labour later on.
  • Increased Maternal Age. I know that 40 is the new 30 (or in my case 48 is the new 38) but unfortunately placentas don’t understand these trends. It seems older mothers’ placentas don’t function as well in late pregnancy as younger women’s placentas.
    A number of high quality large population – based studies have demonstrated that older women (those over 35) have higher stillbirth rates than younger women (remembering that stillbirths are still very rare even for older women) such that for a 40 year old 40 weeks gestation probably has similar risks to 42 weeks for a younger women.
  • Diabetes in pregnancy. This can be either pre-existing diabetes or diabetes that has developed during the pregnancy – so called Gestational Diabetes or GDM. GDM can be treated with diet and exercise or – in more severe cases – insulin injections. We favour IOL before your due date if you have diabetes that requires insulin or your baby is unduly large for dates.

    Even with good treatment diabetes in pregnancy is associated with an increased stillbirth rate and big babies (which are sometimes associated with maternal diabetes) can encounter difficult births so we sometimes wish to induce their births before they become too large.

  • Other Maternal Conditions and Treatments. There are a variety of medical conditions that necessitate induction of labour and birth under closely controlled circumstances. Maternal cardiac defects are one example. Women on blood thinning agents during their pregnancies have to have their births carefully timed around their medication regime, hence the need for IOL.
  • A big baby. Common sense would suggest that if your baby is large (say over 4 kgs or so) it must be much better to give birth to it earlier rather than later (when it has grown even bigger). However this is not necessarily the case and IOL for “a big baby” is very controversial in medical and midwifery circles.

    It is remarkably difficult to assess how big a baby actually in before it is born. Even ultrasound scans can easily be out by 500 grams or more. I did a caesarean on a woman after an ultrasound suggested her baby was 4.5 kg and it (oops) turned out to be 3.5 kg at birth! And while IOL for a big baby might reduce the risk of a difficult vaginal birth (when compared with waiting for natural labour) it does not appear to reduce the risk of a caesarean.

  • Twins. It seems that the risks of stillbirths for twin babies at 38 weeks are about the same for singleton babies at 41 weeks so we generally advise IOL for twins by the time you get to 38 weeks – even if your pregnancy has been straightforward.
    See my Twins information sheet for more information about the birth of twins
  • Fetal problems requiring surgery. Some babies have – for example – cardiac defects that require surgical correction immediately after birth. Accordingly sometimes we have to organise a surgical team (not always an easy task) and ensure the birth occurs on a certain day of the week.

A word about risk

If you read the section above you may be wondering whether anyone has a successful pregnancy without a stillbirth – or worse – occurring. It is important to remember that in all of the situations outlined above the risks – even without IOL – are low in absolute terms (and in some situations we don’t really know what the risks are because of limited – or poor quality – research). To give one example let us look at IOL for postdates pregnancy. The scientific literature supports IOL after 41 weeks on the grounds of a lower risk of the baby dying if you IOL rather than “wait and see”. However you need to conduct 500 IOLs to prevent the death of one baby. So you could easily argue that a “wait and see” approach is quite safe in absolute terms.

So it all depends upon your approach. The vast majority of obstetricians (and I’m VERY guilty here) are extremely conservative and have no wish to take any risks – even small ones – with the welfare of babies if there is a reasonable alternative that eliminates that risk (but remember I’m not the one going through the IOL). This is why IOL rates have increased significantly in the last 20 years or so such that these days more than 25 percent of all births are induced. But before you express outrage at that figure you would do well to remember that – from the baby’s point of view at least – pregnancy and childbirth has also become quantifiably safer over the last 25 years or so.

Even though I am a conservative obstetrician I will always support you if you wish not to be induced in any of the above situations and I will do my best to keep a close eye on you and your baby (or babies) while we wait for spontaneous labour. So from time to time I find myself waiting two, three or more days for labour after a woman’s waters have broken or getting very close to (or beyond) 42 weeks in a pregnancy if that is what she wishes.

A word about Spontaneous Labour (quite a few words, actually)

Before discussing IOL in detail it makes sense to think about the process we are trying to mimic: spontaneous labour. Even with all of the medical knowledge that we have the initiation of labour is comparatively poorly understood (and hence preterm labour and post term pregnancy are similarly mysterious).

Nonetheless we know some things:

  • The baby – not the mother – triggers labour and we think this signal comes from the baby’s brain. The prime candidate for a signal is a hormone produced by the brain called Corticotrophin Releasing Hormone, or CRH. We think CRH is released by the baby’s brain when it is mature and ready to be born.
  • So it seems that fetal CRH somehow initiates the process of labour, although how it actually does this is not clear. This may occur by a number of different mechanisms.
  • Close to the time of birth the mother’s levels of the female hormone Progesterone begin to fall. Progesterone is the hormone produced by the mother’s ovary (up until about 10 weeks gestation) and then the placenta and it function is to keep the baby inside by preventing contractions of the uterus. Treatment with Progesterone pessaries is currently being investigated – promisingly – as a possible treatment to prevent premature labour because of this “uterus – relaxing” effect.
  • At around this time the cervix begins to produce hormones called Prostaglandins (PGs) that have a number of local effects on the cervix. Remember that when you are not pregnant and for the vast majority of your pregnancy is the closed (almost) tube at the bottom of your uterus (and the top of your vagina) that holds your baby in. However in order for your baby to come out the cervix has to soften, shorten and begin to open up (dilate).

    So PGs have the following effects on your cervix:

  • PGs soften your cervix, changing it from a firm texture (like the tip of your nose) to a much softer texture.
  • PGs cause the cervix to become less of a tube, i.e. they shorten the cervix (we call this process effacement).
  • PGs make the cervix begin to open up, or dilate (although dilation really requires contractions of the uterus to “pull” open the cervix).
  • Finally PGs make the uterus much more sensitive to the effects of Oxytocin (see below)
  • At some point in all of this process the mother’s brain begins to produce the hormone Oxytocin. This hormone has a number of effects (including being essential for breastfeeding) but its relevant effect here is that it causes uterine muscle to contract. And so it is the production of Oxytocin – in combination with the uterus’s PG – medicated increased sensitivity to Oxytocin that causes the uterus to contract and begin to dilate the cervix and push the baby downwards.
  • At a very variable point in this process the mother’s waters break – i.e. there is disruption of the membranes surrounding the baby. Again the exact mechanism of this event is a little mysterious and we don’t know why some women’s waters break before labour and – admittedly rarely – some women’s waters never break (yes it is possible to give birth to a baby completely in its sac with the membranes intact). We know that usually (but definitely not always) the waters breaking can either (depending upon the circumstances) help to initiate labour or make uterine contractions stronger, more frequent and more effective. One of the many reasons for this is that amniotic fluid contains PGs which, once released, have all of the effects mentioned above.

So how, exactly, do we Induce Labour?

Well the short answer to this question is that we try to mimic the natural process of the initiation of labour, using precise copies of the natural substances described in the section above.

It is very important to remember that the natural process described above usually takes days or even more than a week. So you need to know that the process of an IOL almost always takes time – often more than a day or so.

We have the following techniques at our disposal in order to induce labour:

  • Prostaglandins. These are usually given as a gel into the vagina in order to “ripen” the cervix (as above). PGs take some time to work so if you need them we usually give you between one and three doses per 24 hours with at least six hours passing between doses (IOL can be a boring process).
  • We can mechanically dilate your cervix by passing a catheter with a small balloon on the end of it through your cervix and then blowing up the balloon. We then leave the catheter in for twelve hours or so and this usually causes the cervix to begin to dilate.
  • We can break you waters artificially by using a thing called an amnihook. Amnihooks are a lot like crochet hooks (for those of you who know what a crochet hook is). The cervix has to be at least two centimetres dilated before we can physically pass an amnihook through the cervix in order to break the waters. This process sounds uncomfortable but it really shouldn’t be any worse than having an internal examination (I know, I know – an internal exam is bad enough).
  • We can give you Oxytocin through an intravenous drip (there is no other way to give oxytocins). Oxytocin tends not to be effective when your waters have not broken (don’t ask me why this is) so we do not use it if your membranes are intact.

Which techniques we use depend on:

a) the state of your cervix and the condition of your baby before we start the IOL, and
b) the manner in which your body responds to whatever technique we use.

Of course you must remember that spontaneous labour does not always follow a predefined sequence in every case – and so it is with IOL.

To illustrate this point I will outline a few possible scenarios:

  1. If your waters have broken at term and you have not gone into spontaneous labour within 48 hours and your cervix is 2 cm dilated then all we need to do to induce labour is to begin an oxytocin infusion through a drip.
  2. If you are over your due date and your baby is well and your cervix is firmly closed then we need to give you a number of doses of PG gel into the vagina over a day or so in order to make the cervix change. Once the cervix has dilated a little then we will offer to artificially break your waters with the crochet – oops – amnihook. If your contractions do not begin after this then we will need to start oxytocin through a drip.
  3. The scenario in 2, above may however go differently. The PGs may lead to the waters breaking and contractions occurring without the need for oxytocin. The process of IOL can be unpredictable.
  4. If your cervix has dilated a little when we begin your IOL then we will break your waters and – if necessary – use an oxytocin drip. However sometimes breaking your waters alone will be sufficient to get you into labour and you may not require the oxytocin drip.
  5. If we are concerned about your baby’s welfare and its ability to tolerate contractions or you have had a previous caesarean section then we may wish to not use PGs to ripen your cervix. This is because PGs are a little unpredictable in the extent to which they cause contractions of the uterus. Very occasionally PGs can cause very strong contractions that can cause fetal distress or problems with scars on the uterus. Under these circumstances we would prefer to use the catheter method to get your cervix to begin to dilate because the catheter does not cause any contractions.

Monitoring your baby’s welfare during an IOL

It is very important that we carefully monitor your baby’s welfare throughout the whole IOL process. There are two fundamental reasons for this increased vigilance:

  1. In the significant majority of cases the very reason we are performing the IOL is that the baby is at risk of harm. Almost all of the “common reasons for IOL” – postdates, high blood pressure, diabetes, prolonged ruptured membranes, poor placental function etc – are associated with increased rates of fetal distress in labour.
  2. The medications we use to induce labour can all cause strong contractions that can, at times, provoke fetal distress.

Accordingly we are keen to keep a close eye on your baby’s welfare throughout the IOL process. Broadly speaking this means that we would like your baby’s heart rate to be monitored electronically at the following times:

  1. Before and after we give you PGs (about half an hour beforehand and an hour or so afterwards)
  2. Before and after we break your waters, and
  3. Once you are contracting regularly and painfully when you are on an oxytocins infusion.

Okay, so what are the downsides of IOL?

Well there are quite a few downsides of IOL. Back in the early seventies it was thought that IOL was completely safe and had no adverse effects on the mother or the baby so the concept of “Elective Induction at Term” became popular – amongst obstetricians at least (no more pesky weekend deliveries!). However not only this approach was unacceptable to women but the hazards of IOL became apparent.

The first downside of IOL is failure. Sometimes we simply can’t get someone into labour despite our best efforts (and the passage of a couple of days). If this occurs we are all in a difficult position. Our options are then to persist and keep trying, stop the IOL and send you home (which is counter intuitive if we feel you or your baby are better off with your baby out), or perform a caesarean section. I find myself performing caesars under this circumstance because:

  • The woman and her partner are so completely fed up by the process that they will have a Caesar just to get the whole experience over with, and
  • We (the patient and I) agree that we would never forgive ourselves if we stopped the IOL and then something bad happened to the baby later on while the baby was still in the uterus.

I guess this means that we should not embark on an IOL unless we are prepared to do a caesarean if we cannot get you into labour. This means that the medical reason for your IOL or your wish to have your baby out should be sufficiently strong for us to accept that if we fail a caesarean should be at least strongly considered.

To some extent we can predict the likelihood of a failed IOL occurring in any given IOL. Factors that suggest a low chance of a failed IOL include:

  • If you have given birth vaginally before,
  • If your cervix has already started to ripen (soften, shorten and begin to dilate),
  • If your baby is low down (engaged) and in a good position (the anterior – as opposed to posterior position),
  • If your baby is normally grown, and
  • If your baby is in good condition.

I suppose this brings us neatly to the issue of the influence of IOL on your chances of having a caesarean birth (don’t worry, I’m getting to pain and pain relief soon). There is absolutely no doubt that – when compared with women who go into labour spontaneously – women whose labours are induced have higher rates of caesarean childbirth. In fact as rule of thumb I would say that women who are induced have double the caesar rate of those who labour spontaneously. This means that for first time mothers the Caesar rate is about 15% with spontaneous labour and about 30% if they are induced. For women who have previously given birth vaginally the comparable figures are about three percent and six percent, respectively.

Again the factors in the bullet point list above are those most associated with a lower chance of a Caesar occurring in any IOL.


– and this is a BIG however (hence the capital letters) – many people forget what is obvious with a little thought. Women whose labours are induced are different – often very different – to women who labour spontaneously. It is absurd to compare the obstetric prospects of a woman who has an uncomplicated pregnancy, a normally grown baby that engaged at 37 weeks, is in the anterior position and is well nourished with someone who is 41 weeks pregnant with a big (4+ kg) unengaged baby in the posterior position. The former woman is far more likely to labour spontaneously before or around her due date and not require a caesarean (or an epidural, for that matter) than the latter.

Or (putting it another way) it is interesting to note that in many of the situations in the “Common Reasons for IOL” section at the start of this sheet your chances of a caesarean are high regardless of whether your labour in induced or not. In fact in a few of the situations mentioned above IOL has been demonstrated scientifically NOT to alter the risk of a Caesar occurring. These situations are IOL for a big baby, postdates pregnancy and when the waters have broken at term without labour occurring. In other situations (maternal diabetes and high blood pressure, for example) women are at increased risk of a caesarean even if they are not induced. And finally if your placenta is feeding your baby poorly there is a high(ish) chance of your baby not tolerating contractions of the uterus and needing a Caesar regardless of whether those contractions were started naturally or artificially.

Notwithstanding the above three or so paragraphs some (but not all) studies that have looked at IOL for absolutely no medical reason (we’re back to Footballers wives and others) have demonstrated higher rates of caesarean section than for spontaneous labour. So we’re left with accepting that IOL per se is associated with an increased risk of caesarean childbirth although that effect is likely to be smaller than the raw figures might suggest.

OK let’s talk (or write) about pain and pain relief. The most common feedback we receive about IOL is that the process can be extremely painful and this is true. IOL – particularly with Oxytocin – can be very painful and epidurals (and their consequences – the topic of another information sheet) are commonly required during IOLs. This does not mean that having an epidural is inevitable when you are induced – in fact quite the contrary. I have had quite a number of women (more than a handful) get through the whole process without needing an epidural. It is also worth mentioning that there is one good thing about Oxytocin: because it is infused through a drip we can adjust the dose we give you. I use a comparatively low dose of oxytocins and I build the dose up slowly and I am prepared to slow the Oxytocin rate down or even stop it as your “natural” contractions intensify.

Remember also that spontaneous labour is also bloody painful!

More specific risks of IOL

In addition to the issues outlined above we always need to remember that pretty much any procedure or drug has an element of risk even if that risk is extremely unlikely (and crossing the road is not without risk).

The risks of prostaglandins (PGs). PGs can rarely cause a fever, shortness of breath and diarrhoea. PGs are a little unpredictable in their effect. Sometimes we can give PGs to a woman and find that she is incredibly sensitive to PGs and begins to have very strong contractions of the uterus almost immediately. This possibility is the reason we NEVER give PGs to a woman with a previous caesarean section – the strong contractions can cause the scar on the uterus to rupture with potentially catastrophic consequences.

The risks of artificially breaking your waters. If your baby’s head is high (not engaged) when we break your waters the umbilical cord can come down into the vagina with the gush of amniotic fluid. While this is very rare (and we tend not to break your waters when the baby’s head is high) we have to perform an immediate caesarean before the baby’s head can compress the umbilical cord. Incredibly rarely when we break the waters we can disrupt a blood vessel running through the membranes (this is called a vasa praevia). If this occurs we will need to perform a caesarean urgently.

The risks of using Oxytocin. As I have mentioned above Oxytocin may cause very strong painful contractions that can, in turn, distress the baby. We can usually manage this situation by stopping the Oxytocin infusion or giving a medicine that can relax the uterus and allow the baby to have a rest from the uterine contractions. If Oxytocin is used for many hours (more than 24) it can cause your urine output to drop and you to retain fluid which can – albeit rarely – have a deleterious effect on some of your blood ingredients.

Advantages of IOL

I suspect that right now you are struggling to see any advantages of being induced. However you need to remember that while IOL is not especially pleasant for the mother it is a safe process for the baby. It is also important to remember that – in the clinical situations outlined in the first section of this sheet – IOL actually improves outcomes for babies by reducing the risk of stillbirths and / or your baby being born in poor condition.

Non Medical Methods of IOL

Another method of induction is sweeping of the membranes. I suppose that this is kind of a medical method because it involves your doctor or midwife performing an internal examination of your cervix. This is when the amniotic membrane is gently separated from the cervix with a gloved finger. The body responds to this by increasing the amount of natural prostaglandin it produces, and this softens and dilates the cervix and can be enough to start labour. Scientific studies have shown that performing an internal examination with sweeping of the membranes significantly reduces the chances of medical IOL being required. The disadvantages are that such an internal examination is uncomfortable and that you can pass a small amount of blood after the examination (although this blood comes from the cervix and does not reflect a problem for your baby).

‘Alternative’ methods of induction

Over the years, there’s been a plethora of other ideas about how to induce labour, some coming from the scientific community and others from the lay community. Some of these have been tested in formal research studies, so it’s worth having a look at the objective evidence. Remember of course that it is very common for women to go into spontaneous labour particularly after their due date so they often attribute their labour to whatever they tried most recently.

One method is sexual intercourse: it’s been suggested that prostaglandin found in semen may soften the cervix, and that the physical stimulation of the lower part of the uterus might bring on contractions. Though it seems to make sense in theory, whether it actually works is a separate issue, and the jury is officially out on this one.

Acupuncture is often considered to be helpful although I am not aware of objective evidence that supports such a claim.

Likewise, castor oil (taken orally) has been used to induce labour since ancient Egyptian times, but recent studies can neither confirm nor deny its usefulness, though they do show that all women who try it become nauseous. There’s also insufficient evidence for the use of acupuncture in inducing labour.

Finally, some studies have looked at induction by breast stimulation. The conclusion is that it may have some benefit in women with a favourable (i.e. soft, dilated) cervix.

If you have any questions or concerns about induction of labour, please do not hesitate to contact me.


This information sheet was drafted by my colleague Dr Alex Owen. I have edited it and made some additions. As always I take full responsibility for any omissions or errors.

Dr Rob