Birth outcomes in plus size pregnancy

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

And another study has suggested 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.

Ellekjaer et al’s (2017) research 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.

Their findings echo the concerns of many of those involved in the care of women of size.

“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.”


These authors’ findings are different from some of the research that has been published in this area.

They offer some interesting suggestions as to why this might be.

“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.”


It seems pretty clear that we need to revise our understanding of what is happening here.

As Ellekjaer et al (2017) suggest,

“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.”


What we can do to change the attitudes and guidelines which may be causing more harm than good is another question entirely…


The Research

Background: Obesity is increasing among primipara women. We aimed to describe the association between body mass index (BMI) during early-pregnancy and duration of labour in nulliparous women.

Methods: Retrospective observational cohort study of 1885 nulliparous women with a single cephalic presentation from 37 0/7 to 42 6/7 weeks of completed gestation and spontaneous or induced labour at Nordsjællands Hospital, University of Copenhagen, Denmark, in 2011 and 2012.

Total duration of labour and the first and second stages of labour were compared between early-pregnancy normal-weight (BMI <25 kg/m2), overweight (BMI 25–29.9 kg/m2), and obese (BMI ≥30 kg/m2) women. Proportional hazards and multiple logistic regression models were applied.

Results: Early pregnancy BMI classified 1246 (66.1%) women as normal weight, 350 (18.6%) as overweight and 203 (10.8%) as obese. No difference in the duration of total or first stage of active labour was found for overweight (adjusted HR = 1.01, 95% CI 0.88–1.16) or obese (adjusted HR = 1.07, 95% CI 0.90–1.28) compared to normal weight women. Median active labour duration was 5.83 h for normal weight, 6.08 h for overweight and 5.90 h for obese women.

The risk of caesarean delivery increased significantly for overweight and obese compared to normal weight women (odds ratios (OR) 1.62; 95%CI 1.18–2.22 and 1.76; 95%CI 1.20–2.58, respectively). Caesarean deliveries were performed earlier in labour in obese than normal-weight women (HR = 1.80, 95%CI 1.28–2.54).

Conclusion: BMI had no significant effect on total duration of active labour. 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.


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