Objective Appropriate gestational weight gain (GWG) can reduce the risk of adverse maternal and neonatal outcomes. This study aimed to explore the appropriate range of GWG during the second and third trimesters of twin pregnancy, and further explore the relationship between GWG and maternal and neonatal perinatal outcomes in twin pregnancies.

Methods A total of 2 222 pregnant women with twin pregnancies who had prenatal examination and delivery in the Foshan Women and Children Hospital from January 2012 to December 2022 were included in this study. Body mass index (BMI) of pregnant women was calculated based on weight and height in the first trimester. These women were divided into underweight (< 18.5 kg/m²), normal weight (18.5 − 23.9 kg/m²), overweight (24.0 − 27.9 kg/m²) and obesity group (≥ 28.0 kg/m²). According to perinatal outcomes, the low-risk population was determined, and the appropriate range of weekly GWG in the second and third trimesters of pregnancy was calculated using the inter quartile range (IQR) method. According to the appropriate ranges, pregnant women with twin pregnancies were divided into insufficient GWG, appropriate GWG, and excessive GWG. To verify these ranges, logistic regression models were performed based on the perinatal outcomes. Generalized estimation equation (GEE) was used to analyze neonatal outcomes.

Results There were statistically significant differences in nulliparity, chorionicity, and conception method among different BMI groups (all P < 0.05). For perinatal outcomes, there were statistically significant differences in gestational diabetes mellitus (GDM), gestational hypertension (GH), and large for gestational age (LGA) (all P < 0.05). Based on 819 low-risk pregnant women, the appropriate ranges of weekly GWG for the underweight, normal-weight, overweight, and obese groups were 0.579 − 0.808 kg/week, 0.531 − 0.769 kg/week, 0.479 − 0.711 kg/week and 0.430 − 0.679 kg/week, respectively. Multivariable logistic regression model suggested that insufficient GWG increased the risk of preterm birth (PTB) (OR = 1.36, 95% CI: 1.11 − 1.67) and small for gestational age (SGA) (OR = 1.74, 95% CI: 1.34 − 2.27), while excessive GWG increased the risk of pre-eclampsia (OR = 1.82, 95% CI: 1.30 − 2.54), GH (OR = 1.72, 95% CI: 1.04 − 2.86), and LGA (OR = 2.17, 95% CI: 1.52 − 3.11).

Conclusion The results of this study showed that based on the appropriate range of GWG during the second and third trimesters of low-risk populations, excessive or insufficient GWG increases the risk of adverse pregnancy outcomes in pregnant women with twin pregnancies. Strengthening the weight management of pregnant women with twin pregnancies can improve the perinatal health of twin pregnancies.