Who is most at risk of caesarean section?

8650597754_90b5fdda87Who is most at risk of caesarean?

I spotted a fascinating study that I want to share.  It was based on data from the US, but I think its findings are also worthy of attention from practitioners in other countries.

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. (This is 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”.)

Kominariak 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. And their analysis highlighted two key areas. Neither of these areas are breaking news, but in my workshops I talk about the importance of knowing which women are at particular risk from the obstetric paradigm, and this study gives us more information on this key question.

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

8392895811_2367164e25That 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.


Being of size

The second risk factor for caesarean section if you are a first time mum is if you are also a woman of size.

As I have previously discussed, 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.  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 recent 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).  This is another area where we could potentially make a significant difference to individual women as well as the overall caesarean section rate, and 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.


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.


The Research

Objective: To determine risk factors for cesarean delivery in nulliparas at labor admission.

Study Design: Nulliparas with live-born, singleton gestations 37 weeks in spontaneous or induced labor were analyzed from the Consortium on Safe Labor database in a retrospective observational study. Classification and regression tree (CART) and multivariate logistic regression analysis determined risk factors for cesarean delivery.

Result: Of the 66539 nulliparas, 22% had a cesarean delivery. In the CART analysis, the first cervical dilation exam was the first branch followed by body mass index (BMI). Cesarean deliveries occurred in 45%, 25%, 14% and 10% of deliveries at <1, 1 to 3, 4 and 5cm dilated, respectively. The BMI influence was most evident in the <1cm dilation category with 26% of BMI <25kgm−2 and 66% of BMI 40kgm−2 having a cesarean delivery. The fewest cesarean deliveries (5%) occurred in those 5cm and BMI <25kgm−2. In the multivariate regression analysis, first cervical dilation exam <1cm (odds ratio (OR) 5.1, 95% confidence interval (CI): 4.5 to 5.7; reference 5cm) and BMI 40kgm−2 (OR 5.1, 95% CI: 4.6 to 5.7; reference BMI <25.0kgm−2) had the highest odds for cesarean delivery.

Conclusion: Cervical dilation on admission followed by BMI were the two most important risk factors for cesarean delivery identified in both CART and multivariate regression analysis.

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.

photo credits: Fleur D’Ébène via photopin (license) and Backyard Poppies via photopin (license).

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