Although high body mass index (BMI) is associated with adverse birth outcomes, the association with severe maternal morbidity is unclear.
Dr Sarka Lisonkova and colleagues examined the association between prepregnancy BMI and severe maternal morbidity.
The team performed a retrospective population-based cohort study including all singleton hospital births in Washington State, 2004-2013.
The research team obtained demographic data and morbidity diagnoses from linked birth certificates and hospitalization files.
Prepregnancy BMI categories included underweight (<18.5), normal BMI (18.5-24.9), overweight (25.0-29.9), obesity class 1 (30.0-34.9), obesity class 2 (35.0-39.9), and obesity class 3 (≥40).
Composite severe maternal morbidity or mortality included life-threatening conditions and conditions leading to serious sequelae, complications requiring intensive care unit admission, and maternal death.
|Absolute risk increases were 17.6 for overweight women|
|Journal of the American Medical Association|
Overall, the team included 743,630 women in the study.
Prepregnancy BMI was distributed as follows: underweight, 3.2%; normal weight, 47.5%; overweight, 25.8%; obesity class 1, 13.1%; obesity class 2, 6.2%; and obesity class 3, 4.2%.
The research team found that rates of severe maternal morbidity or mortality were 171.5, 143.2, 160.4, 167.9, 178.3 and 202.9 per 10,000 women, respectively.
Adjusted odds ratios were 1.2 for underweight women; 1.1 for overweight women; 1.1 for women with class 1 obesity; 1.2 for women with class 2 obesity; and 1.4 for women with class 3 obesity compared with women with normal BMI.
The team noted that absolute risk increases were 28.8 for underweight women, 17.6 for overweight women, 24.9 for women with class 1 obesity, 35.8 for women with class 2 obesity, and 61.1 for women with class 3 obesity.
Dr Lisonkova's team concludes, "Among pregnant women in Washington State, low and high prepregnancy BMI, compared with normal BMI, were associated with a statistically significant but small absolute increase in severe maternal morbidity or mortality."