[Skip to Content]
[Skip to Content Landing]
Views 1,106
Citations 0
Original Investigation
November 14, 2017

Association Between Prepregnancy Body Mass Index and Severe Maternal Morbidity

Author Affiliations
  • 1Department of Obstetrics and Gynaecology, University of British Columbia and the Children’s and Women’s Hospital and Health Centre of British Columbia, Vancouver, Canada
  • 2School of Population and Public Health, University of British Columbia, Vancouver, Canada
  • 3Department of Medicine, University of British Columbia and Women’s Hospital and Health Centre of British Columbia, Vancouver, Canada
JAMA. 2017;318(18):1777-1786. doi:10.1001/jama.2017.16191
Key Points

Question  Is prepregnancy body mass index (BMI) associated with severe maternal morbidity?

Findings  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).

Meaning  Low and high prepregnancy BMI were associated with a statistically significant but small increase in the risk of severe maternal morbidity or mortality.

Abstract

Importance  Although high body mass index (BMI) is associated with adverse birth outcomes, the association with severe maternal morbidity is unclear.

Objective  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.

Exposures  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).

Results  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.

×