Interacting and joint effects of total gestational weight gain and the patterns on adverse pregnancy outcomes in twin pregnancy: a retrospective study

The pattern of gestational weight gain (GWG) over time may independently influence pregnancy outcomes, yet GWG trajectories in twin pregnancies remain poorly characterized, especially in Chinese populations. This retrospective cohort study included 1012 women with normal-weight twin pregnancies. Total GWG was categorized per Institute of Medicine guidelines. Longitudinal GWG trajectories were identified using latent class trajectory modeling. Logistic regression was used to assess associations of GWG categories and trajectories with adverse outcomes, including gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), preterm birth, low birth weight (LBW) for both twins, and small for gestational age (SGA). Two distinct GWG trajectories were identified: Trajectory 1 (sustained moderate gain, 52.87%) and Trajectory 2 (low early gain followed by pronounced late gain, 47.13%). Compared to adequate total GWG, inadequate gain was associated with higher odds of GDM (aOR = 1.52, 95%CI:1.10–2.09), preterm birth (aOR = 1.79, 95%CI:1.22–1.97), both twins LBW (aOR = 2.12, 95%CI:1.46–3.07), and SGA (aOR = 2.69, 95%CI:1.56–4.63), but lower odds of HDP (aOR = 0.45, 95%CI:0.31–0.64). Excessive GWG was associated with lower GDM odds (aOR = 0.48, 95%CI:0.25–0.95) but higher HDP odds (aOR = 2.01, 95%CI:1.24–3.19). Compared to Trajectory 1, Trajectory 2 was associated with lower GDM risk (aOR = 0.43, 95%CI:0.31–0.58) but higher risks of HDP (aOR = 1.69, 95%CI:1.23–2.31). A significant multiplicative interaction was observed for cesarean delivery. Sensitivity analysis excluding extreme GWG values confirmed the robustness of the primary findings. In twin pregnancies, both the total amount and the trajectory pattern of GWG are independently associated with adverse outcomes. Inadequate total GWG increases the risk of most adverse outcomes, while a “catch-up” trajectory pattern (low early, high late gain) is specifically linked to increased risks of HDP. Prenatal care should consider both quantitative and temporal patterns of weight gain for risk stratification and personalized intervention.