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Objective:To investigate the optimal gestational weight gain (GWG) in dichorionic twin pregnancies.Methods:We conducted a retrospective analysis on 755 uncomplicated dichorionic twin pregnancies delivered at Peking University Third Hospital from August 2011 to December 2019. All participants were classified into three groups according to their pre-pregnancy body mass index (BMI), including underweight (BMI<18.5 kg/m 2, n=40), normal weight (BMI=18.5-24 kg/m 2, n=509), and overweight/obese (BMI≥24 kg/m 2, n=206) groups. Gestational BMI, rate of assisted reproduction, and the velocity of GWG were compared between the three groups using analysis of variance, Chi-square test and Kruskal-Wallis test. Regression model of GWG with the increase of gestational weeks was established using random effects model combined with restricted cubic spline to evaluate the percentiles of maternal weight gain during 4-39 gestational weeks. Results:The median of total GWG in the underweight, normal weight, and overweight/obese groups were noted for 17.0 (15.0-20.5) kg, 17.0 (14.0-21.0) kg, and 15.0 (12.0-20.0) kg, respectively, which decreased with the increase of pre-pregnancy BMI ( χ 2=11.974, P=0.002). The regression model fit well with the weight gain during different gestational weeks, which revealed that the weight gain was slow before 13 weeks of gestation, and kept at a steady speed thereafter, regardless of the pre-pregnancy BMI. The median and quartile ( P25- P75) of weight gain were 17.6 (15.2-20.3) kg, 17.3 (14.7-20.2) kg, and 15.7 (12.9-18.8) kg at 37 weeks in the underweight, normal weight, and overweight/obese groups, respectively. Conclusions:GWG of twin pregnancy changes slowly in the first trimester, and increases at a constant rate after the second trimester regardless of pre-pregnant BMI. Overweight/obese pregnancies have lower GWG.
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Objective To investigate the predictive value of cervical length (CL) measured by transvaginal ultrasound for preterm birth<32 weeks,＜34 weeks in twin pregnancies in the second and the third trimester of pregnancy. Methods A total of 490 twin pregnant women with CL measured by transvaginal ultrasound during the second trimester of pregnancy (20-24 weeks) and the third trimester of pregnancy (28-32 weeks) delivered in Peking University Third Hospital, and Tongzhou Maternal and Child Health Hospital from January 2014 to December 2017 were collected, and 161 cases out of which were measured by CL during both the second trimester and the third trimester of pregnancy. Based on the measured gestational weeks, 427 cases were in the second trimester group and 224 cases in the third trimester group. The predictive value of CL for preterm birth was evaluated by calculating the optimal cut-off point with sensitivity and specificity. Logistic regression analysis was used to assess the relationship between CL and preterm birth after adjusting for confounding factors (age of pregnant women, chorionic status, mulipara, assisted reproductive pregnancy and pre-pregnancy body mass index). Results (1) The median CL of pregnant women in the second trimester group and the third trimester group were 36 mm (33-40 mm) and 28 mm (18-33 mm) respectively. In the second trimester group, 151 cases (35.4%, 151/427) were preterm birth and 276 cases (64.6%, 276/427) were full-term birth; the median CL of preterm and full-term pregnant women were 34 mm (30-37 mm) and 37 mm (34-40 mm), respectively, with significant difference (P<0.01). In the third trimester group, 100 cases (44.6%, 100/224) were preterm birth and 124 cases (55.4%, 124/224) were full-term birth; the median CL of preterm and full-term pregnant women were 22 mm (15-30 mm) and 31 mm (23-34 mm), respectively, with significant difference (P<0.01). (2) Prediction of preterm birth<32 weeks and<34 weeks was performed with CL in the second trimester group. The area under the receiver-operating characteristics curve were 0.78 (95% CI : 0.70-0.86) and 0.71 (95% CI : 0.64-0.79), respectively. The optimal cut-off points were 36.5 mm and 33.5 mm, respectively. After adjusting for confounding factors, CL was inversely associated with preterm birth<32 weeks and<34 weeks of gestation. (3) Prediction of preterm birth <32 weeks and <34 weeks were performed with CL in the third trimester group. The area under the receiver-operating characteristics curve were 0.86 (0.75-0.96) and 0.75 (0.67-0.84), respectively. The optimal cut-off points were 17.5 mm and 18.5 mm, respectively. After adjusting for confounding factors, CL was inversely associated with preterm birth at<32 weeks and<34 weeks of gestation. Conclusions CL measured by transvaginal ultrasound in the second and the third trimester is a good predictor for preterm birth of twin pregnancy. CL≤36.5 mm and≤33.5 mm at 20-24 weeks of gestation could predict preterm birth<32 weeks and<34 weeks respectively. CL≤17.5 mm and≤18.5 mm at 28-32 weeks of gestation could predict preterm birth<32 weeks and<34 weeks respectively.