Associations between prepregnancy body mass index, gestational weight gain, and pregnancy outcomes in women with twin pregnancies: A five-year prospective study

Background The purpose of this project was to investigate the relationship between prepregnancy body mass index (ppBMI), gestational weight gain (GWG), and pregnancy outcomes in women with twin pregnancies. Methods A prospective cohort of 369 women with dichorionic diamniotic twin pregnancies was recruited from 2016 to 2020. According to ppBMI using Chinese BMI classifications, they were categorized into the underweight (BMI < 18.5 kg/m(2)), normal (BMI 18.5-23.9 kg/m(2)), and overweight and obese (BMI >= 24 kg/m(2)) groups. In each ppBMI group, they were divided into two subgroups based on the presence or absence of the complications such as gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), and small for gestational age (SGA). The outcomes including GDM, HDP, and SGA were compared among three ppBMI groups, and the associations of GWG with these outcomes within each ppBMI category were analyzed. Results Twin-pregnant women with overweight and obesity were at increased risks of HDP (aOR = 4.417 [95% CI = 1.826-9.415]) and SGA (2.288 [1.102-4.751]), whereas underweight women were prone to deliver SGA newborns (2.466 [1.157-5.254]). Women with GDM gained less weight during pregnancy than those without GDM within each ppBMI category. For overweight and obese women, greater GWG increased the incidence of HDP (1.235 [1.016-1.500]) and decreased the risk of SGA (0.818 [0.702-0.953]). Conclusions Both ppBMI and GWG in twin-pregnant women were strongly associated with HDP and SGA, but not GDM.