1116: Influence of maternal obesity on risk of major congenital malformations in the US

Abstract

The prevalence of obesity in the US has risen exponentially, increasing pregnancy risks in women of reproductive age. The influence of extremes of maternal obesity on risk of birth defects is not well established. We aim to estimate this risk in the offspring of mothers stratified by pre-pregnancy BMI category. STUDY DESIGN: Population-based retrospective cohort of live births in the US from 2012-2016 birth certificate data. Rates of newborn cardiovascular, musculoskeletal, gastrointestinal, genitourinary and central nervous system defects of normal weight women (BMI 18.5 to < 25) were compared to overweight (BMI 25 to < 30), obesity classes I (30 to < 35), II (35 to < 40), III (>/¼40), as well as strata of severe obesity (BMI 40 to < 50, 50 to < 60 and >/¼ 60). Multivariate logistic regression quantified the relationship between maternal BMI and birth defect risk after adjustment for pregestational diabetes mellitus, late prenatal care, maternal race and maternal smoking. RESULTS: Of the 19,844,580 live births in the study period, maternal obesity rates were 3.4%, 23.4%, 12.5%, 23.4%, 12.5%, 6% and 4.2%, respectively for underweight, overweight, and obesity classes I, II and III. Increasing maternal BMI and particularly morbid obesity (BMI >/¼40) was associated with increased rates of all birth defects except gastroschisis. The most robust relative risk increases were observed in defects of the musculoskeletal and central nervous systems, see figure. Increasing maternal BMIs were associated with decreased risk of gastroschisis. Maternal BMI had no significant influence on chromosomal abnormality. CONCLUSION: Risks of any major congenital malformation or multiple malformations, except for gastroschisis, progressively increase with increasing maternal BMIs and specifically with morbid obesity. For obese women who are planning pregnancy, efforts should be made to optimize BMI prior to pregnancy to decrease risk of birth defects.