Birth outcomes in plus size pregnancy

We clearly have more to learn and understand about birth outcomes in plus size pregnancy.

But one thing is clear. 

Several studies indicate that the differences in birth outcomes experienced in plus size pregnancy may be due as much to provider attitudes and biases as to any intrinsic difference or disadvantage.

I have written at length about this in my book Plus Size Pregnancy: what the evidence really says about higher BMI and birth.

And you may have read my post on labour progress myths.

Today, I want to look at another study which helped us to understand why we need to pay attention to the effect of weight stigma on birth outcomes.

A Danish study

In a study in Denmark, Ellekjaer et al (2017) looked at the records of 1885 women who gave birth at term to a single, head-down baby at one hospital in Copenhagen.

Among other things, they compared the length of labour and the type of birth that overweight and non-overweight women experienced.

Now, we know that many people say that women with a higher BMI have longer labours. And there is evidence to show that they have a higher chance of being told they need a caesarean.

But remember that these are not objective measures. Measuring the length and progress of labour is notoriously personal and subjective. And caesareans are the result of a clinical decision.

Let’s see what Ellekjaer et al (2017) found…


The first finding that is of interest to us is that, “BMI had no significant effect on total duration of active labour.” (Ellekjaer et al 2017)

This is an important and useful finding. It questions the assumption that women with a higher BMI have longer labours.

As these authors explain, it’s complicated, because a number of factors may be involved.

In fact, they offer some insight by discussing their findings within the context of previous research.

“A few previous studies suggested no association between labour progression and increasing BMI.

A British study of 8350 nulliparous women compared labour progression in obese versus non-obese women, observing no significant difference within the first or second stages of labour [8].

Contrary to our findings, a majority of previous studies report an independent effect of BMI on total duration of active labour. These studies specifically identify the duration of the first stage of labour as being increased, further supporting an overall increase in labour duration [9, 10, 11, 13, 14, 15].

A study by Kominiarek et al. included 118,978 nulli- and multiparous women in separate analyses. This study found a significant increase in total duration of labour with increasing BMI among nulliparous women [11]. However, the definition of active labour differed from that of most other studies, as a cervical dilatation of only 1 cm was accepted when defining the onset of labour, thereby including what was considered as the latent phase in the current study.” (Ellekjaer et al 2017).

In other words, it may be that the findings of other studies are influenced by the point at which labour is deemed to begin. Or, in fact, by a number of other things. This is why it’s always important to think about the way in which research studies were conducted, rather than just looking at their findings.

Further concerns

But Ellekjaer et al (2017) found something else very important, and their discussion of this finding echoes the concerns of many of those involved in the care of women with a higher BMI.

“Risk of caesarean delivery increased with increasing BMI. Caesarean deliveries are undertaken earlier in obese women compared to normal weight women following the onset of active labour, shortening the total duration of active labour.” (Ellekjaer et al 2017).

As the authors wrote:

“We found that obese women were granted fewer hours of active labour before a caesarean was performed compared with women of normal weight. This could be explained by a possible earlier onset of labour complications within the obese population. However, since there was no difference in the numbers within the different levels of emergency caesareans, this seems unlikely. Alternatively, an increased consciousness amongst healthcare staff concerning the issue of maternal obesity may have had an indirect influence on treatment. A more cautious approach to managing these women might have been unknowingly adopted, resulting in an earlier decision to perform a caesarean delivery.” (Ellekjaer et al 2017).

I have discussed elsewhere how we know that providers treat larger women differently. and this may partly or wholly explain the reason for the increased caesarean rates in women with a higher BMI.

In a nutshell, the reason that larger women are more likely to end up with a caesarean isn’t necessarily because of their body shape, weight, or size, but because of the attitudes of health professionals, the additional tests and interventions they are told they need, and/or the restrictions that are placed upon them by the application of fatphobic and weight biased obstetric guidelines.

But Ellekjaer et al (2017) also point out that it’s really hard to know whether the findings about length of labour are relevant or not, because, as in their finding above, labour is sometimes being shortened because a caesarean is carried out.

Why we need to explore this further

It’s so clear that the current approach isn’t helpful to women with a higher BMI. (It’s arguable whether it’s helpful to other women too, but that’s not the topic of this blog post.)

It’s also very clear that we need to take a closer and more open-minded look at what is happening. Because it’s hard to know what woman’s bodies are capable of when they are birthing predominantly in rule-driven, bureaucratically-focused obstetric units which take a one-size-fits-all, guideline-led approach founded on principles that are often misogynistic, fatphobic and lacking an evidence base.

This is exactly what I’ve looked at in my Plus Size Pregnancy book.

So I am delighted to see that it is helping women and families to become informed about the issues.

Because it’s very clear that the current approach isn’t evidence-based, effective, or respectful.

Ellekjaer et al (2017) suggest that, “Defining the normal progression of labour for overweight and obese women can help eradicate non-scientific misconceptions about the influence of obesity, resulting in more appropriate treatment of women in this weight group.”

I agree with that to some extent. I think it’s good to understand the different things that can impact someone’s experience of labour and birth. But so many aspects of modern maternity care get in the way of our physiology and progress. I do think it is critical, in this day and age, to become informed before you enter a maternity care system or facility, so that you can make the decisions that are right for you.

But one size never fits all, and that might be the most important thing of all.

I discussed some earlier studies on the same topic in this blog post:

Ellekjaer KL, Bergholt T and Løkkegaard E (2017). Maternal obesity and its effect on labour duration in nulliparous women: a retrospective observational cohort study. BMC Pregnancy and Childbirth:222. DOI: 10.1186/s12884-017-1413-6

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