Influence of Maternal Body Mass Index on Severe Maternal Morbidity in the United States [ID: 1383260

Abstract

INTRODUCTION: Rates of severe maternal morbidity (SMM) and maternal obesity are increasing in the United States. We aimed to quantify the influence of increasing maternal body mass index (BMI) on SMM at a population level among U.S. births. METHODS: This was a population-based retrospective cohort study of all singleton live births using U.S.-linked birth–death data from 2013 to 2017. The exposure variable, maternal BMI, was categorized as BMI less than 18, 18–24 (referent), 25–29.9, 30–34.9, 35–39.9, 40–49.9, 50–59.9, and 60–69.9. The primary outcome, SMM, was defined as a composite variable of any blood transfusion, uterine rupture, unplanned hysterectomy, eclampsia, or maternal intensive care unit admission during the delivery hospitalization of the parturient. Generalized linear modeling quantified the association between maternal prepregnancy BMI and SMM while adjusting for maternal race and low socioeconomic status (SES) (Medicaid). Rates of SMM per 10,000 live births and relative risks (95% CI) are reported stratified by BMI. RESULTS: The study population included 19,844,580 live births. The numbers of births stratified by maternal BMI are shown in the table. The lowest rate of SMM was among the normal BMI group (0.57%), with 57 cases per 10,000 live births. The rate and risk of SMM increased with each increasing class of maternal BMI, with the highest rate in the BMI 60–69 category (2.2%), 217 cases per 10,000 live births. Maternal BMI 60–69 experienced the highest risk of SMM, over a threefold increase, even after accounting for the confounding influence of maternal race and low SES. CONCLUSION: Very high maternal BMIs are associated with a high rate and risk of SMM. These findings highlight the importance of addressing this modifiable risk factor on a population basis. Public health initiatives aimed to educate women with obesity of childbearing age about weight loss before pursuing pregnancy could help to mitigate maternal mortality in the United States.