Pre-pregnancy maternal obesity, macrosomia, and risk of stillbirth: A population-based study

Objective: An examination of the synergistic effects of maternal obesity and macrosomia on the risk of stillbirth is lacking. The purpose of this study was to determine the association between fetal macrosomia, maternal obesity, and the risk of stillbirth.

Methods: This retrospective cross-sectional study used the CDC's Birth Data and Fetal Death Data files for 2014-2017 [n = 10,043,398‬ total births; including 48,799 stillbirths]. The exposure was fetal macrosomia stratified by obesity subtypes (I-III). The outcome was the risk of stillbirth. We also controlled for potential and known confounding factors in adjusted models. Adjusted Relative Risks (ARR) were estimated with log-binomial regression models.

Results: The rate of stillbirth was higher among macrosomic infants born to mothers with obesity compared to those without (6.55 vs. 0.54 per 1000 total births). After controlling for confounding, women with obesity types II and III were at increased risk for stillbirth [Obesity II ARR = 2.37 (2.07-2.72); Obesity III ARR = 9.06 (7.61-10.78)].

Conclusions for practice: Obesity-related fetal overgrowth is a significant risk factor for stillbirth, especially among women with type II and type III obesity. This finding highlights the need for more effective clinical and public health strategies to address pre-pregnancy obesity and to optimize gestational weight gain.