Supplementary Material for: Associations between gestational weight gain adequacy and neonatal outcomes in Tanzania

Introduction: Gestational weight gain (GWG) is associated with fetal and newborn health; however, data from sub-Saharan Africa are limited. Methods: We used data from a prenatal micronutrient supplementation trial among a cohort of HIV-negative pregnant women in Dar es Salaam, Tanzania to estimate the relationships between GWG and newborn outcomes. GWG adequacy was defined as the ratio of the total observed weight gain over the recommended weight gain based on the Institute of Medicine body mass index (BMI)-specific guidelines. Newborn outcomes assessed were: stillbirth, perinatal death, preterm birth, low birthweight, macrosomia, small-for-gestational age (SGA), large-for-gestational age (LGA), stunting at birth, and microcephaly. Modified Poisson regressions with robust standard error were used to estimate the relative risk of newborn outcomes as a function of GWG adequacy. Results: Of 7561 women included in this study, 51% had severely inadequate (<70%) or inadequate GWG (70-90%), 31% had adequate GWG (90-125%), and 18% had excessive GWG (≥125%). Compared to adequate GWG, severely inadequate GWG was associated with a higher risk of low birthweight, SGA, stunting at birth, and microcephaly; whereas excessive GWG was associated with a higher risk of LGA and macrosomia. Conclusion: Interventions to support optimal gestational weight gain are needed and are likely to improve newborn outcomes.