Gestational weight gain in twin pregnancies and its association with maternal and neonatal outcomes

Objective To investigate the optimal gestational weight gain (GWG) in twin pregnancies and to analyze the impact of GWG on pregnant outcomes. Methods A retrospective cohort study of twin pregnancies was conducted on women who gave birth in International Peace Maternity and Child Health Hospital, Shanghai Jiaotong University School of Medicine from January 1, 2012 to the June 30, 2015. An optimal range of GWG was calculated based on the amount of weight gain in 711 subjects who gave birth to normal twins and with uncomplicated pregnancy. Another 504 twin pregnant women without gestational complications were recruited for further analysis of the relationship between GWG and gestational outcomes. T-test, analysis of variance and Chi-square test were used for statistical analysis. Results (1) The optimal range of GWG for full-term twin-pregnancy was 15.3-21.4 kg. In those with low body mass index (BMI, <18.5), normal BMI (≥18.5-<25.0) and overweight/obesity (≥25.0), the GWG [M (P25-P75)] were 18.5 (15.8-22.2), 18.3 (15.3-21.3) and 18.1 (14.9-21.5) kg, respectively. There was no significant difference in GWG among those groups (F=0.121, P=0.886). (2) According to the optimal GWG mentioned above, we divided the 504 cases into three groups, including lower GWG group (less than the optimal GWG, n=137), normal GWG group (in the GWG range, n=238) and higher GWG group (more than the optimal GWG, n=129). The neonatal birth weights in the three groups were (2 626.1±225.8), (2 680.1±237.9) and (2 751.9±257.1) g (F=9.189, P<0.01), respectively, indicating that neonatal birth weight was increased by increasing GWG. The proportion of both twins with birth weights of more than 2 500 g was slightly increased, but there was no significant difference among the three groups [51.1% (70/137), 60.5% (144/238) and 64.3% (83/129), respectively, χ2=5.279, P=0.071]. The incidence of gestational diabetes mellitus (GDM) was reduced along with increased GWG [31.4% (43/137), 14.7% (35/238) and 9.3% (12/129), respectively, χ2=25.144, P<0.01], while the incidence of hypertensive disorders in pregnancy (HDP, including gestational hypertension and preeclampsia) in the three groups showed no significant difference. There were 90 cases (17.8%) of GDM in the 504 cases with a pre-pregnancy BMI of 22.5±2.8, which was higher than that of the non-GDM cases (21.2±2.9), (t=3.735, P<0.01). Among the 504 cases, there were 67 cases (13.3%) of HDP (including gestational hypertension and preeclampsia) with a pre-pregnancy BMI of 22.4±2.8, which was higher than that of the non-HDP patients (21.3±2.9, t=2.767, P=0.006). Conclusions The pre-pregnancy BMI has little influence on GWG in twin pregnancies. Increasing GWG to the recommended optimal range or above, and within a certain range, could promote an increase in neonatal birth weight without adding the risks of gestational complications, such as gestational diabetes mellitus, gestational hypertension and preeclampsia. Key words: Pregnancy, twin; Weight gain; Body mass index; Pregnancy outcome