Objective: To explore the optimal gestational weight gain (GWG) of twin pregnant women with different pre-pregnancy body mass index (BMI) through the range of uncomplicated twin pregnant women. Methods: We divided pregnant women with twin pregnancies who delivered in Chongqing Maternal and Child Health Care Hospital into excellent outcome group and poor outcome group. Then

according to the pre-pregnant BMI

they were classified as underweight (BMI<18.5 kg/m2)

normal (18.5≤BMI<24.0 kg/m2)

overweight (24.0≤BMI<28.0 kg/m2)

and obese (BMI≥28.0 kg/m2). We used two methods to determine the optimal range of GWG. The first was a statistics-based approach: calculating the interquartile range of GWG for different BMIs in the excellent outcome group. The second method was the outcome-based method. To verify the rationality of optimal weekly GWG

we calculated the GWG rate (GWGR

total gestational weight gain/gestational weeks) and compared the incidence of maternal complications within and outside the optimal GWGR. Results: The optimal GWG calculated in this study was lower than the GWG recommended by the Institute of Medicine (IOM). Except for the obese group

the overall incidence in the other three BMI groups within the optimal GWG was lower than that outside the optimal GWG. Insufficient GWGR increased the risk of gestational diabetes

premature rupture of membranes

preterm birth

and fetal growth restriction. Excessive GWGR increases the risk of gestational hypertension and preeclampsia. Conclusion: Due to the limited sample size

except for the obese group

we provide preliminary recommendations for the optimal GWG in double chorionic twin pregnancies in China (16.0-21.0 kg for underweight

14.5-21.0 kg for normal

and 13.0-20.0 kg for overweight).