In Australia 26% of labours are induced. The most common reason for induction is a ‘prolonged pregnancy’. That’s an awful lot of babies outstaying their welcome and requiring eviction. I am not going to get stuck into the concept of a ‘due date’ and how accurate or not they are, otherwise this will be a very long post. I also think the EDD (estimated date of delivery) is here to stay – it is deeply embedded in our culture and health care system. You can read about the history of timelines in birth here. This post will focus on induction for ‘prolonged’ pregnancy and the complexities of risk.
A quick word about risk
I don’t particularly like the concept of ‘risk’ in birth. There are all kinds of problems associated with providing care based on risk rather than on individual women. However, risk along with ‘due dates’ is here to stay, and women usually want to know about risks. Risk is a very personal concept and different women will consider different risks to be significant to them. Everything we do in life involves risk. So when considering whether to do X or Y there is no ‘risk free’ option. All women can do is choose the option with the risks they are most willing to take. However, in order to make a decision women need adequate information about the risks involved in each option. If a health care provider fails to provide adequate information they could be faced with legal action. Induction for prolonged pregnancy is not right or wrong if the choice is made by a woman who has an understanding of all the options and associated risks. As a midwife I am ‘with woman’ regardless of her choices. It is my job to share information and support decisions – not to judge.
What is a prolonged pregnancy?
Before we go any further lets get some definitions clear:
- Term (as in a ‘normal’ and healthy gestation period): is from 37 weeks to 42 weeks.
- Post dates: the pregnancy has continued beyond the decided due date ie. is over 40 weeks.
- Post term: the pregnancy has continued beyond term ie. 42+ weeks.
The World Health Organization’s definition of a ‘prolonged pregnancy’ is one that has continued beyond 42 weeks ie. is post term. I am pretty sure that this was not the definition used when collecting the above induction rate statistics because most hospitals have a policy of induction at 41 weeks which is before a prolonged pregnancy has occurred. Very few women experience a prolonged pregnancy. In Australia less than 1% of pregnancies continue beyond 42 weeks and become post-term.
The idea of a prolonged pregnancy also assumes that we all gestate our babies for the same length of time. It seems that genetic differences may influence what is a ‘normal’ gestation time for a particular woman. Morken, Melve and Skjaerven (2011) found “a familial factor related to recurrence of prolonged pregnancy across generations and both mother and father seem to contribute.” Therefore, if the women in your family gestate for 42 weeks so might you. The length of gestation may also be influenced by factors such as diet (McAlpine et al. 2016)
There is still little known about what exactly initiates labour. However, science suggests that the baby secretes surfactant protein and platelet-activating factor into the amniotic fluid as the lungs become mature (Mendelson 2009; Science Daily). This results in an inflammatory response in the mother’s uterus that initiates labour.
The risks associated with waiting
In theory after term (ie. 42 weeks) the placenta starts to shut down. There is no evidence to support this notion. There is also a good physiological explanation of the development and ageing of the placenta here, which concludes that: “There is, in fact, no logical reason for believing that the placenta, which is a fetal organ, should age while the other fetal organs do not…” I have seen signs of placental shut down (ie. calcification) in placentas at 37 weeks and I have seen big juicy healthy placentas at 43 weeks. There is also the idea that the baby will grow huge and the skull will calcify making moulding (when the bones in the baby’s skull adjust), and therefore birth difficult. Again there is no evidence to support this theory and babies are pretty good at finding their way out of their mothers expandable pelvis. It is interesting that these two common assumptions about post-term pregnancy contradict each other. If the placenta stops functioning, how does the baby continue to grow so well?
The real concern with waiting beyond 41 weeks is the increased chance of the baby dying (perinatal death). And women need these statistics in order to make an informed decision. A Cochrane review summarises the quantitative research examining induction vs waiting: “There were fewer baby deaths when a labour induction policy was implemented after 41 completed weeks or later.” However, it goes on to say: “…such deaths were rare with either policy…the absolute risk is extremely small. Women should be appropriately counselled on both the relative and absolute risks.” Hands up all the women who had a discussion with their care provider about the relative and absolute risks of waiting vs induction… hmmm thought so.
Essentially according to the available research, if you are induced at 41 weeks your baby is less likely to die during, or soon after birth. However, the chance of your baby dying is small either way – less than 1%… or 30 out of every 10,000 for those waiting vs 3:10,000 for those induced. This research article reports the relative and absolute risk of stillbirth at various gestations with waiting vs induction. The authors state that 1476 women would need to have an induction to prevent 1 stillbirth at 41 weeks gestation. The substantial increase in risk occurs at 42 week onwards with a stillbirth rate of 1 in 1000 (Decker 2016).
Reviews are only as good as the research they review and there are some concerns about the quality of the available research. The World Health Organization recommends induction after 41 weeks based on this review but acknowledges the evidence is “low-quality evidence. Weak recommendation”. Another review of the literature in the Journal of Perinatal Medicine (Mandruzzato et al. 2010) concluded: “It is not possible to give a specific gestational age at which an otherwise uncomplicated pregnancy should be induced.”
One of the main problems with quantitative research is that it rarely answers the question ‘why’, and rather focuses on ‘what’ (happens). For example, congenital abnormalities of the baby and placenta are associated with post-term pregnancy and this may account for the increased risk rather than the length of gestation (Mandruzzato et al. 2010). Quantitative research also takes a general perspective rather than addressing the risk for an individual woman in a particular situation. For example, is the prolonged pregnancy as sign of pathology or does this woman come from a family of women who have a longer gestation timeframe?
Anyhow – to pretend there are no risks associated with prolonged pregnancy (in general) is not helpful for women trying to make decisions about their options. These general risks should be part of the information a woman uses to decide what is best for her.
The risks associated with induction
It can be difficult to untangle and isolate the risks involved with induction because usually more than one risk factor is occurring at once (eg. syntocinon, CTG, epidural). I did attempt to create a mind map but it ended up looking like a spider had spun a web while under the influence. So I have stuck to a written version:
Risks associated with the actual procedure of induction
The induction process is a fairly invasive procedure which usually involves some or all of the following (you can read more about the process of induction here). There are a number of minor side effects associated with these medications/procedures (eg. nausea, discomfort etc.) There are also some major risks:
- Prostaglandins (prostin E2 or cervidil) to ripen the cervix: hyperstimulation resulting in fetal distress and c-section.
- Rupturing the membranes: fetal distress and c-section (see previous post)
- IV syntocinon / pitocin: Mother – rupture of uterus; post partum haemorrhage; water intoxication leading to convulsions, coma and/or death; reduced breastfeeding rates; increased postpartum depression/anxiety. Baby – hypoxic brain damage; neonatal jaundice; neonatal retinal haemorrhage; death. There is also research suggesting that there may be a link between the use of syntocinon/pitocin for induction and ADHD (Gregory et al. 2013; Kurth & Haussmann 2011). For mothers syntocinon/pitocin is associated with reduced breastfeeding and increased depression and anxiety at 2 months postpartum (Gu et al. 2015).
The most extreme of these risks are rare, but fetal distress and c-section are fairly common. The potential effects of uterine hyperstimulation on the baby are well known (Simpson & James 2008)- which is why continuous fetal monitoring is recommended during induction. This may also explain the association between induction and cerebral palsy (Elkamil et al. 2010)
Risks associated with factors that commonly occur during an induction
The Cochrane review (above) and 2 more recent reviews (Mishanina et al. 2014; Wood et al. 2014) found reduced rates of c-section for women who were induced. This is an interesting finding and does not fit with my observations. I don’t have room in this post to provide a full critique of this research – you can find one by Sara Wickham here.
One major problem with the reviews is that the findings did not distinguish between first time mothers and women who have birthed before. And they are a different kettles of fish. A research study by Ehrenthal et al. (2010) found an increased c-section rate of 20% for women being induced with their first baby. They concluded that: “Labor induction is significantly associated with a cesarean delivery among nulliparous women at term… reducing the use of elective labor induction may lead to decreased rates of cesarean delivery for a population.” Another study by Selo-Ojeme et al (2011) found induction increased the chance of a c-section x3 for first time mothers. The researchers recommend that “Nulliparous [first baby] women should be made aware of this, as well as potential risks of expectant management during counselling.” It is now well established that there are significant risks associated with c-section for both mother and baby. Childbirth Connection provide an extensive and evidence based list.
Induced labour is usually more painful than a physiological labour. Syntocinon (aka pitocin) produces strong contractions often without the gentle build up and endorphin release of natural contractions. In addition unlike natural oxytocin, syntocinon does not cross the blood-brain barrier to create the spaced-out, relaxed feelings that help women to cope with pain (see previous post). Not surprisingly, first time mothers are more than 3x more likely to opt for an epidural (Selo-Ojeme et al. 2011) during an induction. A Cochrane review found that: “Women who used epidurals were more likely to have a longer delivery (second stage of labour), needed their labour contractions stimulated with oxytocin, experienced very low blood pressure, were unable to move for a period of time after the birth (motor blockage), had problems passing urine (fluid retention) and suffered fever and association between epidural analgesia and instrumental birth.” The review also found an increased risk of instrumental delivery, and c-section for fetal distress with an epidural.
There are significant risks associated with ventouse and forceps birth, both for the mother and baby – RANZCOG lists them here. And the risks of c-section available via the link ‘Childbirth Connection’ above. The study by Selo-Ojeme et al. (2011) also found induction = increased risk of uterine hyperstimulation; ‘suspicious’ fetal heart rate tracings; and haemorrhage following birth. Not surprisingly ‘babies born to mothers who had an induction were significantly more likely to have an Apgar score of <5 at 5mins and an arterial cord pH of <7.0’ (basically not in a good way on arrival). Another recent study by Elkamil et al (2011) ‘found that labour induction at term was associated with excess risk of bilateral spastic CP [cerebral palsy]..’ Remember we are inducing labour to prevent harm to the baby…
Again, these general risks need to be individualised for a woman. For example, if this is her first baby, induction significantly increases her chance of a c-section. If this is a subsequent baby then her chance of c-section is not increased… but her chance of uterine rupture is.
The experience of labour
Once again the Cochrane review states: “Women’s experiences and opinions about these choices have not been adequately evaluated.” This is becoming a theme across Cochrane reviews. However, one thing is certain – choosing induction will totally alter your birth experience and the options open to you. Women need to know that agreeing to induction means agreeing to continuous monitoring and an IV drip, which will limit movement. Induced contractions are usually more painful than natural contractions and the inability to move and/or use warm water (shower or bath) reduces the ability to cope. The result is that an epidural may be needed. An induced birth is not a physiological birth and requires monitoring (vaginal exams) and time frames. Basically you have bought a ticket on the intervention rollercoaster. For many women this is fine and worth the risk, but I encounter too many women who are unprepared for the level of intervention required during an induction.
There have been some studies examining women’s experience of induction. Heimstad et al. (2007) conducted a survey of women randomised to immediate induction at 41 weeks or waiting with regular ‘fetal surveillance’. They found that women preferred induction. However, these were women who were allocated an option rather than chose one. Another survey by Childbirth Connection asked mothers about their experience of induction (not necessarily for prolonged pregnancy) – 17% of those induced felt they were under pressure to do so by health care professionals. The quotes from women make interesting reading too. A study by Hildingsson et al. (2011) found that labour induction was associated with a less positive birth experience, and women who were induced were more likely to be frightened that their baby would be damaged during birth. However, again this research was not limited to induction for prolonged pregnancy therefore the women may have had genuine pregnancy complications requiring induction.
A more recent UK study by Henderson and Redshaw (2013) found that “women who were induced were generally less satisfied with aspects of their care and significantly less likely to have a normal delivery. In the qualitative analysis the main themes that emerged concerned delay, staff short- ages, neglect, pain and anxiety in relation to getting the induction started and once it was underway; and in relation to failed induction, the main themes were plans not being followed, wasted effort and pain, and feeling let down and disappointed.”. A German study (Schwarz et al. 2016) concluded that: “women’s expectations and needs regarding IOL are widely unmet in current clinical practice… and that “there is a need for evidence-based information and decisional support for pregnant women who need to decide how to proceed once term is reached.”
Alternatives to waiting or medical induction
Before labour begins the uterus and cervix need to make physiological changes ready to respond to contractions. It is now thought that the baby is the controller of the labour ‘on’ switch. So, the baby signals to the mother that he/she is ready, oxytocin is released and the uterus responds. In comparison to other mammals, humans have the most variable gestation lengths. This suggests that other factors such as environment and emotions (eg. anxiety) also influence the start of labour. This would make sense considering what we know about the function of oxytocin (see previous post). It is also something most midwives are aware of – a stressed out mother is more likely to go post term than a relaxed and chilled out mother. Having said that, post term is probably the normal gestation length for many women regardless of what is going on. Creating anxiety and stress around due dates and impending induction is probably counter productive to labour.
There are a number of ‘alternative’ or ‘natural’ induction methods available (BellyBelly covers most of them here). However, an induction is an induction. Trying to force the body/baby to do something it is not ready to do is an intervention whether it is with medicine, herbs, therapies, techniques… or anything else. Interventions of any kind can have unwanted effects and consequences. At least a medical induction takes place with close monitoring of mother and baby with access to medical support if a complication arises. I worry that alternative inductions do not have this level of monitoring or back up.
However, ‘interventions’ (massage, acupuncture, etc.) that are aimed at relaxing the mother and fostering trust, patience and acceptance may assist the body/baby to initiate labour if the physiological changes have already taken place.
A significant minority of babies will not be born by 41 weeks gestation. Whilst the definition of a prolonged pregnancy is 42 weeks+, induction is usually suggested during the 41st week. Women need to be given adequate information about the risks and benefits involved with either waiting or inducing in order to make the choice that is right for them. There is no risk free option. The risk of perinatal death is extremely small for both options. I know women who have lost a baby in the 41st week of pregnancy, and women who have lost a baby as a result of the induction process. For first time mothers the induction process poses particular risks for themselves and their babies. Each individual woman must decide which set of risks she is most willing to take – and be supported in her choice.
You can read more about induction in my book Why Induction Matters
Maternity Choices information sheet for parents.
Sara Wickham – post-term pregnancy and induction of labour resources
Sara Wickham – ten things I wish every women knew about induction of labour
Sara Wickham – How to cancel a labour induction?
A news article: ‘I was pregnant for 10 months’