Reasons you may be offered an induction of labour

Reasons you may be offered an induction of labour 

The following circumstances in pregnancy may result in an induction of labour being offered to you:

• Post-dates pregnancy
• Advanced maternal age (40 years of age or more)
• Suspected big baby
• Suspected small baby
• Diabetes
• Pre-eclampsia
• Reduced fetal movements
• IVF
• If your waters break before tightenings start
• Obstetric Cholestasis

Skip to the factsheet that is relevant to you, so you can start to make a fully informed decision on whether you would like an induction of labour. 

Post-dates pregnancy

A term pregnancy is classed as anything between 37 and 42 weeks. The reason induction is offered to women later on in their pregnancy is because the general rate of perinatal death (stillbirth and early infant death) increases after 42 weeks: 

• At 40-41 weeks you are 99.9% likely to have a live baby
• At 42 weeks you are 99.7% likely to have a live baby
• At 43 weeks you are 99.5% likely to have a live baby (ref. 13) 

A review of evidence has found that induction of labour for women before they reach 42 weeks has reduced the perinatal death rate from 0.3% to 0.03%, therefore induction of labour has now become a recommendation for all women at this point in pregnancy. A woman’s estimated due date is either worked out by calculating 40 weeks since her last menstrual period (LMP) or by an ultrasound dating scan. Unfortunately, even with a reliable LMP date and dating scan, it is still not completely accurate (ref. 14). Many factors contribute towards how long a woman’s pregnancy will last; longer pregnancies tend to run in families (ref. 15) and the length of her menstrual cycle will also have a bearing (ref. 16). 

The reason for the increased chance of stillbirth isn’t known and there are mixed opinions about it. There is evidence to say the placenta changes towards the end of pregnancy.  Some researchers think that the placenta deteriorates with age (ref. 17), whilst others think that the placenta changes and adapts to meet the needs of the growing baby (ref. 18). Studies of placentas in women who have had post-dates pregnancies, show no indications that the function of the placenta depletes with time (ref. 19) and in the studies trying to find out the reason for the increased risk of stillbirth, placentas were not found to be a contributing factor (ref. 20). Congenital abnormalilites may be a reason for a prolonged pregnancy, as this was found on 1/3 of stillborn babies that were prolonged pregnancies. 

Every woman will experience a different pregnancy length, which may well be normal for her. If a woman has previously had a post dates pregnancy without complications then she isn’t at increased risk if she chooses to wait for labour to begin by itself (ref. 21). For a first time mother, it is essential to consider what may be normal for her, for example, if prolonged pregnancies run in the family, if there are any other unique factors in her pregnancy, for example Mother and baby’s wellbeing. 

Of women who choose to wait for labour to start by itself, 90% will have had their babies by 42 weeks and 99% will have had their baby by 43 weeks. If you decide that induction isn’t for you and you would rather wait for labour to start, additional monitoring of baby will be offered to you. This monitoring may include CTG monitoring and/or ultrasound scans. This can show baby’s wellbeing at the time of the monitoring. Some women will find additional monitoring is reassuring while others will find it stressful and anxiety inducing, therefore it would not be beneficial in helping labour to start. The most valuable assessment of your baby’s wellbeing is their movements, if you have any concerns that your baby’s movement pattern has changed, reduced or is excessive then please call triage. 

Advanced maternal age

If you are aged 35 years or older, then you are part of this category of women. It has been found that women over 35 years old, after 39 weeks, the chance of stillbirth slightly increases: 

• Women over 40 years old at 39 weeks – chance of stillbirth is 0.2% (99.8% chance of having live baby)
• Women under 35 years old at 39 weeks – chance of stillbirth is 0.1% (99.9% chance of having live baby)
• However if a woman is 40 years old and 42 weeks pregnant the chance increases to 1% (99% chance of having live baby) (ref. 22). 

There is no clear explanation of this increased chance of stillbirth. One possible explanation is that due to their age, women may have a more varied medical history and also their chance of having a baby with a congenital variation is more likely (ref. 23). Women with health complications or who had IVF were not separated out from women without complications in studies, this makes it difficult to define whether healthy women who are older actually have any higher chance of stillbirth than someone who does have health conditions. Due to the above statistics, Women aged 40 or over are offered an induction at 39 weeks as per RCOG guidance (ref 23). Since RCOG made this recommendation, a new study has been carried out which showed no significant reduction in stillbirth when inducing for maternal age at 39 weeks but did show a 20-30% increased chance of having a caesarean section, a 10% increased risk of instrumental birth and an increased chance of mothers and baby’s being re-admitted back to hospital within 28 days (ref 24). The same study did show a reduction from 0.26% to 0.08% of stillbirth if women were induced at 40 weeks. 

Wye Valley NHS Trust currently offer an induction of labour for advanced maternal age between 40-41 weeks of pregnancy. 

Suspected large baby

The definition of a big baby (sometimes called macrosomic) is if they weigh more than 4kg at birth (8lb, 13oz). Of all UK births, 1 in 10 babies fall into this category. 

Estimating a baby’s weight is problematic, as there is no accurate way of measuring baby’s weight before they are born. When your midwife measures your bump this can be incorrect half of the time due to varying factors such as your BMI and baby’s position (ref 25). If it is suspected that your baby may be larger, the best way to find out a more accurate weight is to carry out an ultrasound scan however there is still an inaccuracy rate of 15% (ref 26). As an example, if the scan estimated your baby to weigh 3200g (7lb 0oz), the weight could be anything from 2720g (5lb 9oz) to 3680g (8lb 11oz). This inevitably results in some women being told they are carrying a big baby when they are not. 

Your baby’s weight will be determined by different natural factors, for example, if big babies run in your family or how many weeks you are when you give birth; if you birth your baby at 41 weeks, it is likely to be heavier than if it was born at 37 weeks, due to having some extra growing time. 

There are also medical reasons why your baby may be measuring big; women with gestational diabetes are much more likely to have a large baby – this is discussed on the Induction for GDM page further on. 

Healthcare providers tend to be concerned about the possibility of a shoulder dystocia when baby is suspected to be big. Shoulder dystocia is when the baby’s shoulder becomes stuck on the front of the mother’s pelvis once the head is born, and stops the rest of the baby being born. This is an emergency as baby’s cord is being compressed once the head is born and it requires the caregiver to encourage the mother to adopt a different position and possibly do some internal manuevres (inserting fingers to try and dislodge the shoulder). This can sometimes cause injuries to the baby and be a traumatic experience for the woman. 

NICE guidelines on inducing labour for a suspected large baby, currently say that women should be informed of all options on how to birth their baby (wait for labour, be offered an induction or caesarean section) and they state that the rate of shoulder dystocia is less when women are induced. However, the evidence for this was of low quality and included women who had diabetes (having diabetes in pregnancy is known to increase the chance of shoulder dystocia). When taking out the women who had diabetes, there was then no difference between the occurrence of shoulder dystocia for women who had an induction compared to women who didn’t (ref 27). 

The problem is that if a woman is known to be carrying a large baby she is more likely to be offered intervention, which can in turn contribute to shoulder dystocia.

An example of this was demonstrated in a study, which compared the outcomes of women who were diagnosed as carrying a large baby compared to women who birthed a large baby without it being diagnosed in pregnancy (ref 28). The results of the study showed that if women were diagnosed as carrying a large baby they were: 3 times more likely to choose an induction or caesarean 4 times more likely to have significant perineal tearing, more likely to have a postpartum haemorrhage (excessive bleeding). 

If your baby is suspected as being large for gestational age, it is unlikely that baby will become too big to be born vaginally if your pregnancy continues at term, as the percentage of large for dates baby’s changes very little during the last few weeks of pregnancy.  It is estimated that 11% of babies are macrosomic at 38 weeks of pregnancy and this rises to 14% at week 40, these findings were found through a study of women whose BMI was high and therefore had a higher chance of growing a macrosomic baby anyway (ref 29). 

Stillbirth statistics for large babies

• Babies plotting between the 91st and 97th centile during pregnancy the chance of stillbirth is 0.1%
• Babies plotting on 98th centile or above during pregnancy, the chance of stillbirth is 2% 

A rise in stillbirth can be seen in babies on or over the 98th centile.  However, the studies that helped to develop these statistics did not differentiate between healthy pregnancies and those affected by diabetes, which can increase the chance of stillbirth. Another study confirms how knowing a baby is large can influence how the labour is managed by concluding that caregivers are much more likely to diagnose labour dystocia (a lack of progress in labour). This then increases the chance of interventions and the associated risks with it (ref 30). 

As you can see, the evidence behind induction for large babies isn’t clear. Therefore if it is thought that your baby may be measuring over the 97th centile, it is important that you have a full discussion with your midwife or obstetrician to work out what is individually best for you. 

Suspected small baby

You may hear two different terms when you have been told your baby may be smaller than average: 

Small for gestational age - this describes a baby who is plotting beneath the 10th centile on their growth chart. It can be normal for some babies to be small, particularly if both the baby’s mother and father are small. However for some babies who are small, it may be caused by: 

Fetal Growth Restriction (FGR) - describes a baby who is struggling to grow to their potential, due to their placenta not working properly and therefore not supplying them with the nutrients and oxygen needed to grow adequately. The placenta may not be working properly if the mother has pre-eclampsia, is undernourished, smokes, misuses substances or has severe anaemia. Caregivers are concerned about baby’s who are diagnosed as FGR because it is known that it increases their chance of stillbirth and neonatal death (death after birth). 

It is really important that as many FGR babies are diagnosed as possible because once diagnosed, their outcome significantly improves, with stillbirth reducing from 1.9% to 0.9%. 

FGR is diagnosed through a scan which will look at baby’s growth, the amount of fluid around baby and an umbilical doppler, which shows how effective the blood flow from the placenta to baby is. If this blood flow is observed as being particularly abnormal, it is advised that your baby is born immediately, even if they aren’t term (ref 23). There isn’t a way of making your placenta work better while baby is still in the womb, therefore if your baby is affected by FGR, then the doctor will be discussing the timing of the birth and whether it is better to try and keep your pregnancy going a little longer or whether it is better that baby is born as soon as possible. 

However if there are no particular concerns then the aim will be for you to reach 39 weeks gestation (Saving Babies Lives Care Bundle, 2016). Babies affected by FGR may not tolerate labour very well, this is because during a tightening, the blood flow from the placenta is temporarily disrupted. For a baby without FGR the blood flow between tightenings would compensate for this, but for a baby affected by FGR they are more likely to become distressed. Induction of labour can create stronger tightenings than when labour starts on its own, therefore if baby is severely FGR your doctor may suggest that a caesarean section would be safer for baby, this advice is supported by NICE guidelines (ref 24). 

Gestational Diabetes

If you have been diagnosed with gestational diabetes, it is because it has been found that you have a higher than normal level of glucose (sugar) in your bloodstream. It is called gestational diabetes because it has been found whilst you are pregnant. In a small amount of cases, it may be that a woman has undiagnosed diabetes, not caused by pregnancy. The only way to know this is after baby is born; if your blood glucose remains high or uncontrolled postnatally then it is likely you have type 2 diabetes, your GP will check this at your 8 week postnatal check. 

Diabetes is when the insulin in your body is unable to unlock the glucose from your cells and use it as energy, therefore the glucose in your bloodstream builds up. Women are more likely to become diabetic during pregnancy because from around 20 weeks gestation the growth hormones produced by the placenta, which encourage baby to grow can slow down the production of insulin. To compensate for this your pancreas will release more insulin, however in some women, this doesn’t happen very effectively, meaning there isn’t enough insulin to release the energy from the glucose you ingest. Some women will be diagnosed with gestational diabetes and manage to keep their blood glucose levels within normal limits by a change in diet and lifestyle. However, some women will struggle to control their blood glucose levels and will need insulin tablets or injections. 

The risks associated with gestational diabetes are difficult to determine for these two sets of women because the majority of research that has been carried out has not separated the two groups. However, it is known that the risk comes with uncontrolled blood glucose levels; not simply with the diagnosis of being gestational diabetic. If a woman manages to keep her blood glucose levels in a normal range then she is at no more chance of experiencing a complicated pregnancy and birth than a woman who does not have gestational diabetes. 

One of the main concerns that caregivers have about women with gestational diabetes is that baby will grow too big. If the mother has high glucose levels this will go through to baby. Baby will then produce more insulin than normal to help break the glucose down. A consequence of this is that baby’s organs will grow more and will lay down more fat around his/hers upper body and shoulders. This in turn increases the chance of shoulder dystocia; shoulder dystocia is when the baby’s shoulder becomes stuck on the front of the mother’s pelvis once the head is born, and stops the rest of the baby being born. This is an emergency as baby’s cord is being compressed once the head is born and it requires the caregiver to encourage the mother to adopt a different position and possibly do some internal manoeuvres (inserting fingers to try and dislodge the shoulder). This can sometimes cause injuries to the baby and be a traumatic experience for the woman. 

Women with gestational diabetes who have normal blood glucose levels

If you have normal blood glucose levels throughout your pregnancy, you are not at risk of baby growing too big as baby is not receiving excess levels of glucose through the placenta. The World Health Organisation advise that women with normal blood glucose levels should not be offered an induction of labour or caesarean section (31), whereas NICE guidelines advise women to have given birth by 40+6 (ref 32), however the evidence used by NICE doesn’t differentiate for normal and abnormal glucose levels. 

Women with high blood glucose levels

If you have uncontrolled blood glucose levels, this can make other conditions in pregnancy more likely, pre-eclampsia is one of these. If this is true in your case, please also read the information sheet on pre-eclampsia. It also makes the likelihood of developing type 2 diabetes later on in life, higher. As detailed above, the main risk for baby is that baby may be big and the chance of shoulder dystocia happening is increased. The insulin can delay the production of surfactant – this is an important substance that baby produces to help their lungs inflate. Therefore some babies born to mother’s with high blood glucose levels can have some problems breathing after birth, especially if they have been induced at an earlier gestation or been born by elective caesarean section. 

Pre-eclampsia

Pre-eclampsia usually isn’t diagnosed until at least 20 weeks of pregnancy, but it actually starts early on. If the blood vessels in your placenta don’t embed properly into your womb, it means the blood flow from the placenta to baby isn’t as optimal as usual. Your body tries to compensate for this by tightening all the blood vessels in your body, in order to send more blood to baby. This in turn increases your blood pressure and eventually the blood vessel walls will start to become damaged, creating small holes. These holes let some fluids from your bloodstream leak out into your tissues, which in turn can cause swelling. This swelling is typically seen in your face, hands, feet and legs. Your body tries to fix these holes by releasing protein into your bloodstream, but this protein also leaks out through the holes in the blood vessel walls, some of this protein then comes out when you urinate. This is why your midwife tests your urine and takes your blood pressure at every appointment and if pre-eclampsia is suspected from these results, then a further assessments will be offered to help confirm the diagnosis. If you then go on to experience severe headaches, visual disturbances, nausea, or pain at the top right part of your tummy (liver pain) then it could be a sign that the pre-eclampsia has developed further. 

These signs rarely develop before 20 weeks of pregnancy but are more common towards the end of pregnancy. If pre-eclampsia becomes severe, then it can cause seizures, bleeding on the brain and liver and kidney failure. The only cure for pre-eclampsia is for the baby to be born. If you are over 37 weeks you will be offered delivery by induction of labour or caesarean section, if you are under 37 weeks then the risks of continuing the pregnancy will be weighed up against the risks of pre term birth. Induction of labour for pre-eclampsia is the same process, however you may need additional medications in order to help control your blood pressure and reduce the chances of seizures. 

Reduced fetal movements

Reduced fetal movements describes a reduction in the usual amount of movements your baby makes, a loss of movements or weaker movements. There are a few reasons why you might feel your baby’s movements have changed, if baby is in a different position, if you are in a different position or where the position of your placenta is, for example, if your placenta is at the front of your tummy then you might feel less movements (ref 33). 

You will probably have started to feel your baby move from around 16 to 20 weeks of pregnancy and from around 32 weeks you may have noticed a particular pattern of movements. Your baby should continue with their pattern of movements up until they are born, there is no evidence to say movements slow down prior to going into labour (ref 33). 

Up to 40% of women will report having reduced fetal movements at some point in their pregnancy and of these women, 70% will have no further concerns or complications. Because of this, induction is not offered for women with one episode of reduced fetal movements when the baby is growing well and there are no other concerns (ref 33). 

If you do have concerns, it is important that you ring triage and come in for monitoring. Your baby’s wellbeing will be analysed on a CTG monitor (if you are over 26 weeks) and/or by ultrasound scan, which looks at baby’s growth, blood flow from the placenta to baby and the amniotic fluid around baby. Fetal movements are an important indicator of a baby’s wellbeing, if baby is regularly having episodes where they’re not moving as much, it can be a sign that they are saving their energy due to growth restriction, their placenta isn’t working very well or there are congenital abnormalities (ref 33). There isn’t any evidence that telsl us whether it is better to be induced when a woman is experiencing recurrent reduced movements, however the RCOG advise that a woman’s pregnancy and wellbeing should be taken into account when deciding whether an induction of labour should be offered, for example if there are concerns about baby’s growth or placental function. 

If your waters break before you go into labour

If you are 37 weeks or more and your waters have broken but you’re not experiencing any contractions, then your midwife/doctor may be discussing the chance of infection to you and baby and/or offering you an induction of labour. This situation happens to around 10% of all pregnant women, here are a few statistics of what then happens to these women:  

• 79% of women will then go into labour within 12 hours of their waters breaking
• 95% of women will go into labour within 24 hours of their waters breaking (ref 34).

NICE guidelines currently advise that women are offered an induction of labour within 24 hours of their waters breaking, this is because the chance of infection to mother and baby rise slightly; for women whose waters haven’t gone, the chance of an infection in their womb is 0.5%, for women whose waters have broken, the chance of an infection can rise to 1% (99% of women will not develop and infection). You can therefore opt to be induced if you have not started tightening 18-24 hours after your waters have broken. 

If you are known to be carrying Group B Streptoccous (GBS) then you will be encouraged to start this process straight away and commence antibiotics, due to the additional risk of infection to baby. A review of studies that have looked into whether it is better to wait for labour to start or to be induced after their waters had broken, concluded that for the women who were induced, there may be less babies born with an infection (ref 34). This rise was less than 2% and included babies with suspected infections and definite infections. 

The problem with this is that when a woman’s waters have broken, the people looking after her will always be looking for a potential infection, meaning suspected infections may be overestimated and once the potential infections were taken out of the results, there wasn’t a difference in the rate of infections between the two groups. Potential infections may be overestimated as during an induction certain aspects of the process can cause the woman to have a raised temperature, for example, epidurals, prostaglandins (hormones used to induce labour) or dehydration. The review also flagged up that the studies were all of low quality. There was a study of moderate quality, which showed that there was no difference in the rate of babies who died when comparing the two groups. When a baby is born the midwife uses a scoring system called ‘The Apgar Score’, it is an assessment of their breathing, colour, tone, heartrate and reflexes. As part of the review of evidence, the APGAR scores were compared between women who had chosen induction and women who had chosen to wait for labour. There was no difference between the two groups. If a baby had an infection, it is likely that their Apgar scores would be poor. But again, these results come from studies which were classed as poor quality. Antibiotics may be suggested if your waters have broken, you’re not in labour and you are showing signs of infection. A review of evidence suggests it is not advised to give antibiotics without signs of infection, as the long term effects of antibiotics for mother and baby are not known. 

Signs of infection can be a temperature, pain in your womb, feeling unwell, smelly vaginal discharge or the water draining being smelly. To help reduce your chances of developing an infection, avoid sexual intercourse and try to keep vaginal examinations to a minimum. Once baby is born, skin to skin helps to provide baby with your helpful bacteria and protect against infection (ref 35). 

IVF

If you have conceived your pregnancy through IVF, then you may have been advised that it is safer to induce your labour at term because the risk of stillbirth is higher for you. 

Some studies suggest that the chance of stillbirth is increased when a pregnancy has been conceived through IVF (ref 36,37). The actual increase in risk varies widely, depending on which research study you read. 

A Danish study concluded that the risk increased from 0.37% for a person experiencing an unassisted conception, to 1.62% for a person who has undergone IVF. It has been debated as to whether the findings from studies looking into IVF and stillbirth may be distorted because they did not account for the fact that many women undergoing IVF may be older, and may have pre exisitng health conditions. This study states that age has accounted for. Importantly, it didn’t state at which stage these stillbirths happened. 

It is known that women who have had IVF are more likely to experience a pre-term birth (3) and if these births are extremely pre-term then the chance of mortality is higher. The rate of stillbirth between 22/40 and 27+6 is also higher for women who have had IVF (4) but very importantly, it has been found that after 28 weeks, the rate of stillbirth is no different to women who had conceived without assistance. Therefore induction of labour at term, for women who have had IVF would not be beneficial in a pregnancy that has otherwise been straightforward. 

There are some theories that the placenta may not work so well at the end of pregnancy if you have had IVF. There is no evidence that supports this theory.  However, it has been found that for women who have had IVF are more likely to be affected by gestational diabetes, pre-eclampsia, or have a baby who is small or is classed as having intrauterine growth restriction. If one or more of these conditions has affected your pregnancy then please refer to the relevant factsheets in this booklet for more information. If they haven’t affected your pregnancy, then the fact you are more at risk of them is not a valid reason for an induction of labour. However, the obstetricians have agreed to offer induction from 40 weeks if this is something that you wish. 

Obstetric Cholestasis

Obstetric cholestasis (OC) or Intrahepatic cholestasis of pregnancy, affects around 0.7% of pregnancies in a multi-cultural society (ref 38). If you have been diagnosed with this condition, it may have started with itchy skin, which may have been worse on your hands and feet but can be anywhere on your body. It is caused when the bile that flows through your liver slows down or even stops. This leads to bile acids building up in your liver, which then leak out into your bloodstream and cause itching. Some women find that the itching is worse at night, affects their sleep and can lead to problems with emotional wellbeing. Sometimes the itching can be so severe that the skin becomes damaged. Other symptoms can include dark urine, pale stools, fatigue, liver pain (pain in right upper abdomen) and feeling generally unwell. OC isn’t routinely tested for, if you have some of these symptoms then your midwife will ask to take your blood to see what your bile acid levels are and check your liver function. 

It isn’t known exactly why women develop OC but it is thought to be a combination between genetic, hormonal and environmental reasons. Women with pre-eclampsia or with multiple pregnancies are more likely to develop OC. 

The timing of the IOL depends on the level of bile acid in the blood. In cases of severe OC (bile acid more than 40), women are likely to be offered an IOL between 37/40 and 39/40. There is some evidence to say that the chance of stillbirth is increased for women who have severe OC. In milder cases, women will be offered an IOL between 39 and 40 weeks of pregnancy. 

At 36/40 - risk of stillbirth is 0.06% compared to 0.02% in an unaffected pregnancy

At 40/40 - risk of stillbirth is 0.2% compared to 0.06% in an unaffected pregnancy

The chance of premature birth is higher with OC, there is a hypothesis that the bile acids can cause tightenings. Babies born to mothers with OC are also more likely to have meconium in their waters. This is likely to be because of the extra movement of fluid through the bowel which causes baby to open their bowels earlier than normal. Increased bile acids can also disrupt the production of surfactant in baby’s lungs, which helps them to fill their lungs with air at birth and maintain breathing. Because of this more baby’s are admitted to special care when their mother has OC -a rise of 6.4% compared to baby’s born to mothers without OC (ref 39).