Investigation of optimal gestational weight gain for twin pregnancy in Southwest China: a retrospective study

There is a lack of data on gestational weight gain (GWG) in twin pregnancies. We divided all the participants into two subgroups: the excellent outcome subgroup and the adverse outcome subgroup. They were also stratified according to prepregnancy body mass index (BMI): underweight (< 18.5 kg/m2), normal weight (18.5–23.9 kg/m2), overweight (24–27.9 kg/m2), and obese (≥ 28 kg/m2). We used 2 methods to confirm the optimal range of GWG. The first method was a statistical-based method (the interquartile range of GWG in the excellent outcome subgroup). The second method was an outcome-based method that compared the incidence of pregnancy complications in the population below or above the optimal GWG and analysed the relationship between weekly GWG and pregnancy complications to justify the rationality of optimal weekly GWG through logistic regression. The optimal GWG calculated in our study was lower than that recommended by the Institute of Medicine (IOM). Except for the obese group, in the other 3 BMI groups, the overall disease incidence within the recommendation was lower than that outside the recommendation. Insufficient weekly GWG increased the risk of gestational diabetes mellitus, premature rupture of membranes, preterm birth and fetal growth restriction. Excessive weekly GWG increased the risk of gestational hypertension and preeclampsia. The association varied with prepregnancy BMI. We provide preliminary Chinese recommendations for optimal GWG (16-21.5 kg for underweight, 15-21.1 kg for normal weight, 13–20 kg for overweight), except for obesity, due to the limited sample size.