Background: The world is transitioning to an obese future, but few studies have measured the burden of increased maternal body mass index (BMI) on pathological fetal overgrowth, especially the trends in this burden and its heterogeneity in populations with different characteristics. Methods: A population-based retrospective cohort study was conducted with 7,998,620 Chinese females who had participated in the National Free Pre-Pregnancy Check-ups Project and became pregnant during 2013-2017. The proportions of macrosomic and LGA neonates attributable to high BMI (population attributable fraction, PAF) and annual percent change of yearly PAFs were estimated. Results: We found that the burden of macrosomic and LGA (large-for-gestational-age) neonates attributable to high pre-pregnancy BMI increased among Chinese females with planned pregnancies during 2013-2017. The PAF of macrosomia attributable to high BMI increased from 3.16% (95% confidence interval: 2.97-3.35%) to 7.11% (6.79-7.42%) by 23.60% (16.76-30.85%) annually, and the PAF of LGA increased from 2.35% (2.21-2.48%) to 5.00% (4.79-5.21%) by 21.98% (16.14-28.11%) annually. Our study identified that participants with disadvantaged socioeconomic status (including those without higher education, living in provinces with GDP per capita < 40,000 CNY, tier IV, and tier V cities) and residing in northern and southwestern China were at high risk of a rapidly expanding burden. Conclusions: Government authorities should control pre-pregnancy BMI through nationwide intervention programs and direct more resources to focus on the unfair burden on females with disadvantaged socioeconomic status.
Keywords: body mass index; cohort studies; fetal macrosomia; large-for-gestational-age; population attributable fraction.