Is prepregnancy body mass index (BMI) associated with severe maternal morbidity?
In this cohort study that included 743 630 pregnant women in Washington State between 2004 and 2013, low and high prepregnancy BMI, compared with normal BMI, were significantly associated with increased risk of a composite adverse outcome of severe maternal morbidity or mortality that included maternal death and conditions leading to serious sequelae (eg, adjusted absolute risk increase of 28.8 per 10 000 for underweight and 61.1 per 10 000 for class 3 obese women).
Low and high prepregnancy BMI were associated with a statistically significant but small increase in the risk of severe maternal morbidity or mortality.
Although high body mass index (BMI) is associated with adverse birth outcomes, the association with severe maternal morbidity is unclear.
To examine the association between prepregnancy BMI and severe maternal morbidity.
Design, Setting, and Participants
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 (weight in kilograms divided by height in meters squared) 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).
Main Outcomes and Measures
Composite severe maternal morbidity or mortality included life-threatening conditions and conditions leading to serious sequelae (eg, amniotic fluid embolism, hysterectomy), complications requiring intensive care unit admission, and maternal death. Logistic regression was used to obtain adjusted odds ratios (ORs) and adjusted rate differences with 95% confidence intervals, adjusted for confounders (eg, maternal age and parity).
Overall, 743 630 women were included in the study (mean age, 28.1 [SD, 6.0] years; 41.4% nulliparous). 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%. 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 ORs were 1.2 (95% CI, 1.0-1.3) for underweight women; 1.1 (95% CI, 1.1-1.2) for overweight women; 1.1 (95% CI, 1.1-1.2) for women with class 1 obesity; 1.2 (95% CI, 1.1-1.3) for women with class 2 obesity; and 1.4 (95% CI, 1.3-1.5) for women with class 3 obesity compared with women with normal BMI. Absolute risk increases (adjusted rate differences per 10 000 women, compared with women with normal BMI) were 28.8 (95% CI, 12.2-47.2) for underweight women, 17.6 (95% CI, 10.5-25.1) for overweight women, 24.9 (95% CI, 15.7-34.6) for women with class 1 obesity, 35.8 (95% CI, 23.1-49.5) for women with class 2 obesity, and 61.1 (95% CI, 44.8-78.9) for women with class 3 obesity.
Conclusions and Relevance
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.
Sarka Lisonkova, Giulia M. Muraca, Jayson Potts, Jessica Liauw, Wee-Shian Chan, Amanda Skoll, Kenneth I. Lim. Association Between Prepregnancy Body Mass Index and Severe Maternal Morbidity. JAMA. 2017;318(18):1777–1786. doi:10.1001/jama.2017.16191