When you're having a long pregnancy, it can seem like everyone is treating you like you're broken. It can make you feel like something is wrong, like your baby is at risk. Are they at risk? Should you be induced? What are the alternatives?

Defining the terms

The World Health Organisation defines a full term pregnancy as being between 37 and 42 weeks gestation.

ACOG defines a pregnancy between 41 and 41+6 weeks as “late term” and pregnancies that last more than 42 weeks as “postterm”.

The terms “post-dates” and “prolonged pregnancy” are not clearly defined by themselves, and can therefore all be used interchangeably and inconsistently by clinicians. The result can often be confused and upset parents who have seen multiple different health care professionals and been told slightly different things by each one.

To add to the potential confusion is the term “post mature”, which is used to describe a baby who has suffered ill effects from being in utero past 42 weeks.

These terms are not scary by themselves, but them not being explained to parents and then used synonymously by health care professionals, or being used differently by different people in different (or even the same) departments, can lead to parents feeling anxious unnecessarily. In some circumstances, this lack of consistency, combined with issues around consent I will go into later, can cause people to disengage (to a greater or lesser extent) from healthcare services because they feel they cannot be trusted.

Why offer induction, and why then?

It is routine for the vast majority of pregnancies to be induced if they continue into the forty-first week. The actual numbers vary from Trust to Trust – 41+3, 41+5, I’ve even heard of 41 weeks on the dot – but it is not typical for pregnancies to be “allowed” to continue past 42 weeks.

The reason for offering induction at 41-42 weeks is, according to the NICE Clinical Guideline [CG70] Inducing Labour, “to avoid the risks of prolonged pregnancy”.

NICE also state that: “Although the risks of fetal compromise and stillbirth rise steeply after 42 weeks, this rise is from a low baseline. Consequently, only a comparatively small proportion of that population is at particular risk. Because there is no way to precisely identify those pregnancies, delivery currently has to be recommended to all such women.”

Basically, induction is offered to everyone because there are some pregnancies that are at risk of developing complications, but it’s not possible tell in advance which pregnancies those are going to be. Induction can sometimes take a few days, and so for you to have given birth before you reach 42 weeks it is necessary to start the process a few days before that.

Specifically, the concerns around a long pregnancy are to do with the baby’s size, unexplained stillbirth, a reduction in amniotic fluid, meconium and the baby developing post-maturity syndrome.

What are the alternatives?

There are 2 alternatives to induction.

Expectant management is a series of checks which can be done to check on the baby’s health (on top of the normal antenatal checks). They may include an ultrasound to check on the amniotic fluid levels, a scan to check the blood flow through the placenta, and continuous monitoring of the baby’s heart rate and movements over a 20-30 minute period. It is typically offered twice weekly after 42 weeks. If all is well then parents can choose to continue to wait for labour to start. If the checks show up a problem, then it can be discussed and a course of action chosen.

The other option is to wait without having additional checks done.

What does the evidence say?

The answer to that question isn’t a simple one. There are a lot of studies out there which are aimed at studying whether particular interventions are beneficial and when. You could quote a single study and say “this evidence shows this”, but that would be deliberately reductionist. (Reductionism is the action of reducing a complex scenario down to simplistic factors.) It is much more accurate to look at all of the evidence, even the studies which don’t show results that align with your personal viewpoint, and try to determine which of them are relevant to your specific circumstances.

There are studies which show that there are benefits to inducing labour at 41 weeks. There are studies which show that there are benefits to inducing labour earlier than that. There are studies which show that there is no difference between inducing labour at 41 weeks or 42 weeks gestation. There are studies which show a reduction in caesarean rates when induction is carried out when compared to expectant management; something which goes directly against statistics coming directly from hospitals, and midwives and doulas experiences supporting births, which show that induction increases caesarean rates.

It is important to not just take the results of studies at face value and dig further into the study’s methodology to see exactly what was measured and how it was defined (what exactly is “early induction”?), how many participants were included and what their specific circumstances were (are results from 100 women in rural India applicable to a woman in suburban Yorkshire?). Unfortunately that is not always easy; sometimes studies are not fully accessible by lay persons, and the technical jargon can make them difficult to decipher. I will outline some information worth taking into consideration below.

The latest Cochrane review (Cochrane reviews are an analysis of the results of lots of studies), states that induction at or beyond term “is associated with fewer deaths of babies and fewer caesarean sections; but more assisted vaginal births” when compared with expectant management, but that there were “no important differences [...] for most of the other maternal and infant outcomes”. It also states that “the best time to offer induction of labour to women at or beyond term is not yet clear and warrants further investigation”, and is clear that the evidence was of moderate quality at best.

The problem with meta-analyses like the Cochrane reviews is that the results will vary depending on what studies are included. By including or excluding particular studies you can change the overall results. For example, this meta-analysis looked only at studies comparing induction at 41+ weeks with expectant management. The results showed that the only difference was that after induction fewer babies had meconium aspiration syndrome, and all other outcomes (including baby deaths) were not significantly different between the two groups.

AIMS recently published this article which brings together information collected from actual Trusts in the UK for over a decade. The numbers show that the actual incidence of stillbirths and neonatal deaths, which drops as a pregnancy progresses, has largely continued to drop after 40 weeks gestation.

Clearly, this is not predictive, because it cannot look at an individual’s risk factors and work out whether or not they have a higher than average chance of experiencing baby loss. But what it does suggest is that in the UK, on a population basis, the numbers for the last 14 years have not matched up with the results of some clinical trials which suggest a rise in risk.

Another interesting article is this blog post by Sophie Messager around the idea of the failing placenta. Placental aging is one of the most common reasons given to those facing a long pregnancy to choose induction instead of waiting. But is it real?

Well, there is certainly evidence that some placentas do fail to adequately provide nutrients to babies, but that does not necessarily mean that all placentas fail after a particular gestation has been reached. Placentas undergo a lot of changes during their lifespan, but those changes do not necessarily equate to a sudden failure to fulfil their role. The placenta is a foetal organ. It is as much a part of the foetus as their intestines or their spleen. Why would one of their organs suddenly age to the point of critical failure and not the others? What would be the biological explanation that would explain such a phenomenon?

From a clinical point of view, the concern is that parents may lose their baby, or their baby may suffer illness or injury, and that this could have been prevented had they been induced. The existence of this concern isn’t intrinsically a problem. The problem is how those concerns are presented to parents, whether and how evidence is presented for consideration, and how parents’ decisions about their care are received and reacted to.

What does induction involve?

An induction of labour can involve a number of interventions. The typical pathway would be as follows: prostaglandin gel pessary to “ripen” the cervix; ARM – artificial rupture of membranes or having your waters broken; synthetic oxytocin drip which is turned up approximately every half an hour until you are having 4 contractions in 10 minutes.

Some Trusts offer “balloon induction” as an alternative to the gel pessary. This is a mechanical method: a balloon catheter is inserted inside the cervix and filled with sterile water to inflate it. to manually open it. It puts pressure onto the cervix, hopefully stimulating natural production of prostaglandin which ripens the cervix ready for labour. It isn’t offered as standard by most Trusts, but is in some, and in those where it isn’t it may be negotiated for depending on your preferences.

Each step of the process involves risks. Being induced also increases the likelihood of other interventions being needed which carry their own risks, for example, an epidural being sited which may cause headaches, or a caesarean which increases the likelihood of placental abnormalities in future pregnancies. Because of the way that one intervention can lead to another and then another, it is often known as the Cascade of Intervention.

While these risks are well known, they can sometimes be brushed over when discussing induction as an option. There is also a trend towards encouraging more natural methods, or having one or more sweeps, in the hopes that induction will not be necessary.

Natural induction methods

There are a variety of methods which are quoted as being “natural ways to bring labour on”. The most common are: castor oil, clary sage, evening primrose oil, raspberry leaf tea or capsules, spicy curries, long walks, nipple/breast stimulation, sex, pineapple, and alternative therapies (acupuncture, reflexology, aromatherapy).

Evidence Based Birth has covered some of these methods here much more effectively than I could. Suffice it to say, some of them are effective, and some of them are not, and some of them are effective but carry side effects.

Sweeps

A stretch and sweep is the name given to an intervention performed during a vaginal examination, in the hopes that it will give the body a nudge. The cervix is gently stretched, and a finger is run around between the cervix and the amniotic sac to separate them.

Some people feel that sweeps are brilliant. They are relatively harmless, a tiny blip on the intervention spectrum, and sometimes they are all that is needed to get labour started. If nothing happens, well you’ve lost nothing by trying. And if it does, well hooray, you avoided induction! Research has shown that sweeps reduce your likelihood of passing 42 weeks by around half.

Some people feel that sweeps are the thin end of the wedge. If a sweep causes labour to begin you were probably already on the cusp of labour anyway, and there are potential negative effects. For example, it can introduce bacteria (as can anything placed into your vagina), it can be really painful (cervixes are not really keen on being touched), and it can irritate your uterus, causing backache and/or niggly period pains that don’t amount to anything but do interfere with your comfort and sleep.

As with everything else, a sweep is a tool, and it can be useful for some people and not for others. You can read more about them here. As always, the benefits and risks should be discussed beforehand, and valid consent gained.