Having a high or low prepregnancy body mass index was associated with a small absolute increase in severe maternal morbidity and mortality in a large, retrospective cohort study.
Some studies have suggested a link between obesity and pregnancy complications such as preeclampsia, gestational diabetes, thromboembolism, and cesarean delivery. But one study suggested no link between higher BMI and risk of severe morbidity.
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Adjustment for weight gain had no significant effect on the observed associations, Sarka Lisonkova, MD, PhD, of B.C. Women’s Hospital & Health Centre in Vancouver and her colleagues reported in JAMA.
Compared with normal weight women (BMI 18.5-24.9), women considered underweight (BMI less than 18.5) had an adjusted odds ratio (aOR) for mortality or severity morbidity of 1.2 (95% confidence interval, 1.0-1.3). Women who were overweight (BMI of 25.0-29.9) had an aOR of 1.1 (95% CI, 1.1-1.2).
The risk was also greater for women with class 1 obesity (BMI, 30.0-34.9; aOR, 1.1; 95% CI, 1.1-1.2), class 2 obesity (BMI, 35.0-39.9; aOR, 1.2; 95% CI, 1.1-1.3), and class 3 obesity (BMI, 40 or greater; aOR, 1.4; 95% CI, 1.3-1.5).
In all cases, the absolute increases in mortality and severe morbidity, compared with normal weight women, were small, ranging from adjusted rated differences of 17.6 per 10,000 for overweight women to 61.1 per 10,000 women with class 3 obesity. Underweight women had an increase of 28.8 per 10,000.
Specifically, underweight women had a higher risk for antepartum and postpartum hemorrhage and acute renal failure, whereas women who were obese had increased risks for respiratory morbidity and thromboembolism, the researchers reported.
The study was funded by the Canadian Institutes of Health Research. Dr. Lisonkova is supported by an award from the Michael Smith Foundation for Health Research. No other financial disclosures were reported.
SOURCE: Lisonkova S et al. JAMA. 2017 Nov 14;318(18):1777-86.