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.
Retrospective population-based cohort study including all singleton hospital births in Washington State, 2004-2013.
Demographic data and morbidity diagnoses were obtained from linked birth certificates and hospitalization files.
Prepregnancy BMI categories included underweight, normal BMI, overweight, obesity class 1, obesity class 2, and obesity class 3.
|Absolute risk increases were 28.8 for underweight women|
|Journal of the American Medical Association|
The team's 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.
Overall, 743,630 women were included in the study.
The researchers found that prepregnancy BMI was distributed as follows: underweight, 3%; normal weight, 48%; overweight, 26%; obesity class 1, 13%; obesity class 2, 6%; and obesity class 3, 4%.
The team noted 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 research team found 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 comments, "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."