Gestational weight gain and adverse pregnancy outcomes in Chinese women: evaluation of current guidelines and low-risk weight gain ranges

The association between gestational weight gain (GWG) and maternal–infant health is established, but the applicability of current guidelines among women in Northwest China remains unclear. To evaluate associations of GWG with adverse maternal and neonatal outcomes, compare the applicability of IOM and NHC guidelines, and derive potential low-risk GWG ranges. This retrospective cohort included 54,155 singleton pregnancies in Shaanxi (2023–2025). GWG was classified by IOM and NHC guidelines. Multivariable logistic regression evaluated associations, ROC and DCA analyses assessed discriminative ability and clinical net benefit. Restricted cubic spline models with Poisson regression derived low-risk GWG ranges based on the nadir of composite outcome risk (incidence rate ratio increase ≤ 2.5%). Low agreement between guidelines (κ = 0.43). Inadequate GWG increased risks of preterm birth, gestational diabetes mellitus and small for gestational age (adjusted OR1.47–2.05), while excessive GWG increased preeclampsia, gestational hypertension, caesarean delivery and large for gestational age (adjusted OR1.62–2.11). Similar discriminative ability (AUC 0.585–0.606) and clinical net benefit. Non-linear associations were observed ( P < 0.001). Low-risk GWG ranges (normal weight 12.5–16.3 kg) exceeded current recommendations in women with high BMI (overweight 11.8–16.0 vs. 7–11.5 kg; obesity 5.9–12.8 vs. 5–9 kg). Both inadequate and excessive GWG increase adverse outcome risks. The two guidelines showed similar predictive performance but substantial classification discrepancies. Low-risk GWG ranges among women with higher BMI extended beyond current recommendations; however, these ranges require prospective multicentre validation and should not be interpreted as clinical targets or new recommendations.