Association between gestational age specific weight gain in pregnancy and risk of adverse perinatal outcomes: A secondary analysis of the INTERBIO-21st Fetal Study.

BACKGROUND: Gestational Weight gain (GWG) is a potentially modifiable factor that can influence perinatal health outcomes. OBJECTIVES: To investigate the association between gestational age (GA)-specific weight gain and adverse perinatal outcomes. METHODS: This study is a secondary analysis of the INTERBIO-21st Fetal Study, a prospective, longitudinal cohort conducted from February 8, 2012, to November 30, 2019, across six sites in Brazil, Kenya, Pakistan, South Africa, Thailand, and the United Kingdom. A total of 3,354 pregnant women, aged ≥18 years with a Body Mass Index (BMI) <35 kg/m2, initiated antenatal care before 14 weeks' gestation. Weight was measured at 5 ± 1-week intervals from 14 to 40 weeks. GWG was assessed using the GA specific INTERGROWTH-21st and BMI-specific Institute of Medicine (IOM) guidelines. Adverse outcomes included gestational diabetes mellitus (GDM), pregnancy induced hypertension (PIH), emergency caesarean delivery, low birthweight (LBW), preterm birth (PTB), small or large for gestational age (SGA, LGA), macrosomia, and birth length or head circumference (HC) <10th or >90th centile. RESULTS: Inadequate GWG was prevalent, with 53% (n=1,767) below the 25th centile of INTERGROWTH-21st standards and 62% (n=2,079) below IOM guidelines. Compared to GWG between 25th and 75th centile (n=370), females with GWG <25th centile (n=1767) had a higher odds of SGA (Odds ratio, OR=2.7, 95% confidence interval, CI: 2.2, 3.4), birth HC<10th centile (OR= 2.4, 95% CI: 1.8, 3.2), GDM (OR=1.9, 95% CI: 1.3, 2.7), LBW (OR=1.9, 95% CI: 1.5, 2.4), and birth length<10th centile (OR=1.7, 95% CI: 1.4, 2.1). Similarly, females with GWG >75th centile (n=458) had higher odds for emergency caesarean section (OR=1.7, 95% CI: 1.1, 2.7) and PIH (OR= 1.5, 95% CI: 1.1, 1.9). CONCLUSIONS: Appropriate-for-age (AGA) specific GWG between the 25th and 75th centiles standards is associated with reduced adverse outcomes, highlighting the importance of tailored guidelines for optimal maternal and neonatal health.