The Effects of Prepregnancy Body Mass Index and Gestational Weight Gain on Fetal Macrosomia Among American Indian/Alaska Native Women.

Objectives: The American Indian/Alaska Native (AI/AN) population is a high-risk group across many health indicators, including fetal macrosomia. We aimed to investigate the effects of prepregnancy body mass index (BMI) and gestational weight gain (GWG) on macrosomia and explore possible racial and geographical variations among AI/AN women.

Methods: This retrospective cohort study was conducted from the Pregnancy Risk Assessment Monitoring System in eight states (2004-2011) among live, singleton, term births to AI/AN women 20 years or older. Prevalence of macrosomia (birth weight ≥ 4000 g) by select characteristics were estimated; differences were assessed with Chi-squares. Multivariable logistic regression was conducted to calculate adjusted odds ratios (aOR) for effects on macrosomia of BMI and GWG (enumerating the pounds women deviated from the Institute of Medicine guidelines for GWG) controlling for other factors in the total sample and stratified by race and state of residence.

Results: The prevalence of macrosomia was 14 %, ranging from 8 to 21 % (Utah-Alaska). Among AI/AN women, 30 % were obese prepregnancy and 50 % had excess GWG. Significant independent effects were found for macrosomia of prepregnancy overweight (aOR 1.27; 95 % Confidence Interval 1.01-1.59), obesity (aOR 1.63; 1.29-2.07), and excess GWG (aOR 1.16; 1.13-1.20 per five pounds gained beyond appropriate). Adjusted estimates varied between race and state.

Conclusions: Prepregnancy BMI and GWG are independent factors for macrosomia among AI/AN women. Future research should prioritize development, testing, and implementation of weight management programs, which account for variations among AI/AN women, both before and during pregnancy for BMI regulation and GWG control.