Gestational weight gain according to the Brazilian charts and its association with maternal and infant adverse outcomes.

Background: The lack of gestational weight gain (GWG) recommendations for low- and middle-income countries is a significant concern.

Objectives: To identify the ranges on the Brazilian GWG charts associated with lowest risks of selected adverse maternal and infant outcomes.

Methods: Data from 3 large Brazilian datasets were used. Pregnant individuals aged ≥18, without hypertensive disorders or gestational diabetes were included. Total GWG was standardized to gestational age-specific z-scores according to Brazilian GWG charts. A composite infant outcome was defined as the occurrence of any of small-for-gestationa lage (SGA), large-forgestationa lage (LGA), or preterm birth. In a separate sample, postpartum weight retention (PPWR) was measured at 6 and/or 12 mo postpartum. Multiple logistic and Poisson regressions were performed with GWG z-scores as the exposure and individual and composite outcomes. GWG ranges associated with the lowest risk of the composite infant outcome were identified using noninferiority margins.

Results: For the neonatal outcomes, 9500 individuals were included in the sample. For PPWR, 2602 and 7859 individuals were included at 6 and 12 mo postpartum, respectively. Overall, 7.5% of the neonates were SGA, 17.6% LGA, and 10.5% were preterm. Higher GWG z-scores were positively associated with LGA birth, whereas lower z-scores were positively associated with SGA births. The risk of the selected adverse neonatal outcomes were lowest (within 10% of lowest observed risk) when individuals with underweight, normal weight, overweight, or obesity gained between 8.8-12.6; 8.7-12.4; 7.0-8.9; and 5.0-7.2 kg, respectively. These gains correspond to probabilities of PPWR ≥5 kg at 12 mo of 30% for individuals with under and normal weight, and <20% for overweight and obesity.

Conclusions: This study provided evidence to inform new GWG recommendations in Brazil.