Who is most at risk of caesarean section?

Who is most at risk of caesarean?

A few years ago, a fascinating study led me to start exploring this question in a way that wasn’t being considered within many maternity care systems at the time.

It influenced my thinking, leading me to include this topic in workshops, and to explore the evidence further.

I’ve since written about this area in both In Your Own Time and Plus Size Pregnancy, and this blog post is an introduction to the topic.

The researchers’ question was fairly simple, which is often the case with studies that become gems.

Kominiarek et al (2015) undertook a retrospective, observational study in which they analysed the outcomes of women whose birth details had been entered into the Consortium on Safe Labour database.

So yes, the study was based on data from the US, but I think its findings are also worthy of attention from practitioners in other countries.

This is, by the way, the same database that was used by Zhang et al (2010) in the study that led to their recommendation that, “allowing labor to continue for a longer period before 6 cm of cervical dilation may reduce the rate of intrapartum and subsequent repeat cesarean deliveries in the United States”.

Kominiarek et al (2015) had a slightly different question, though.

They wanted to see if they could work out whether there were any ‘risk factors’ which were predictive of caesarean delivery.

What are the ‘risk factors’ for caesarean?

Kominiarek et al‘s (2015) analysis highlighted two key areas. Neither of these areas are breaking news, but this study was one of those which led me to start talking about the importance of knowing which women are at particular risk from the obstetric paradigm.

The bit in italics is the key here. As I have written elsewhere, caesarean isn’t a ‘natural’ or inevitable outcome, but a clinical decision. It is recommended because of a subjective decision made by a human. In some situations (for instance an immediate and life-threatening risk to the mother or baby), almost all humans would agree that a cesarean would be a good idea. But in many other situations (including so-called slow labour progress, suspected large baby, and elective or risk factor-based indications such as where a woman has a higher BMI), there is considerable debate.

The researchers discovered that, in this data set, there were two key risk factors for caesarean section in women having their first baby.

The first risk factor was cervical dilation on admission to hospital. The earlier a woman goes to hospital, the more likely she is to have a caesarean section.

And the more dilated her cervix is when she gets there, the higher her chances are of having a normal birth.


It’s not rocket science

That one isn’t rocket science, and (while we need to bear in mind that this is only an association) we could speculate on some of the reasons why this is the case.

Once a woman is in hospital, she may be less able to move freely, to use certain comfort measures which are available to her at home (such as snuggling in her own bed, relaxing in her own bath or pottering about in her kitchen or garden, where time may seem to pass faster because she isn’t focused on labour and the clock), and she may be more likely to have medical intervention. 

Also, although many women want to be in hospital for birth, their primal brain may not feel as safe there (even just because of the strange smells and the presence of strangers) and this can inhibit labour and/or increase pain, both of which can also lead to interventions.

That’s not to say that women shouldn’t go to hospital if that’s where they want to give birth, of course. But it may explain why it appears that, the sooner you go in, the more likely you are to end up with a caesarean section. And why this is one of the key areas that we need to focus on if we want to help more women to have a normal birth.

The timing of admission to hospital is an area that has been looked at several times in the past few years, and we know it’s not as simple as just saying, stay home as long as possible.  We need to provide appropriate services, information and support so that women have good knowledge and feel that they can do this. But at least we know that placing continued focus on this area could make a difference.

Having a higher BMI

The second risk factor for caesarean section if you are a first time mum is if you have a higher BMI.

As I have discussed elsewhere, the issues in this area are complex and we still have much to learn. But it is becoming ever clearer that it is not appropriate to blame women for their size or to claim that the increased chance of caesarean section which is experienced by women of size is because their bodies are somehow lacking the ability to give birth after experiencing spontaneous, physiological labour. 

In fact, it turns out that practitioners’ pre-existing perceptions may play a part in the poorer outcomes experienced by women of size. A concern which was echoed in a US analysis which noted that:

“…although, “as a mother’s weight increases, the likelihood of a caesarean increases substantially, yet again what we see is a bigger difference in the practice associated with the particular condition than we see in the particular condition…” (Declercq 2015). 

We also know that women with a higher BMI are often denied access to the things that can increase their chances of a physiological birth. These include midwifery-led care, birthing in midwifery-led settings, and using water for labour and/or birth.

This is another area where we could potentially make a significant difference to individual women as well as the overall caesarean section rate.

It’s great to have these kinds of studies adding to our knowledge of who is at risk from intervention, so we can work how to help prevent those caesarean sections that are unnecessary.

But it’s also critical to help more people become aware of the issues.

Caesarean section isn’t a ‘natural’ outcome. It’s the result of a decision, so caesarean section rates are affected by cultural, professional and personal beliefs and attitudes. Someone’s chance of having a caesarean may have more to do with the beliefs of their care provider than their own body. It’s a sobering thought.

If you’d like to learn more about higher BMI and birth, please see my book: Plus Size Pregnancy: what the evidence really says about higher BMI and birth.


Kominiarek MA, VanVeldhuisen P, Gregory K et al (2015). Intrapartum cesarean delivery in nulliparas: risk factors compared by two analytical approaches.  Journal of Perinatology 35(3): 167-172.

Zhang J, Landy HJ, Branch DW et al (2010). Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol. 2010 Dec;116(6):1281-7. doi: 10.1097/AOG.0b013e3181fdef6e.

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