Establishing population-specific gestational weight gain ranges for twin pregnancies and comparing their performance with IOM recommendations: a retrospective cohort study from central China

Objectives To establish optimal pre-pregnancy body mass index (BMI)-specific gestational weight gain (GWG) ranges for twin pregnancies and compare their association with maternal and neonatal adverse outcomes against Institute of Medicine (IOM) recommendations. Design Retrospective cohort study.

Retrospective cohort study. Adjusted ORs (aORs) with 95% CI were used to quantify associations; average marginal effects (AME) with 95% CI (in percentage points) were used to compare absolute risk differences.

Setting Perinatal data from >70 obstetric institutions in Wuhan, China, collected via the Wuhan Maternal and Child Health Service Management Information System. Participants 10 636 women with twin deliveries at ≥28 weeks (2011 - 2023).

Pre-pregnancy BMI categorised using Chinese cut-offs: underweight Primary and secondary outcome measures Hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM), premature rupture of membranes (PROM), small for gestational age (SGA) and large for gestational age. Results Optimal GWG ranges were: underweight 18.0 - 25.0 kg, normal 14.0 - 24.0 kg, overweight 12.2 - 24.0 kg, obesity 13.3 - 20.0 kg.

Compared with IOM guidelines, study-derived ranges showed more favourable risk identification.