Objective::To build a reference fetal growth chart for the Chinese population based on fetal ultrasound measurements.Methods::This was a multicenter, population-based retrospective cohort study. Longitudinal ultrasound measurement data were collected from 24 hospitals in 18 provinces of China from 1 st September through 31 st October of 2019. The estimated fetal weight (EFW) was calculated based on head circumference, abdominal circumference, and femur length using Hadlock formula 3. Fetal growth curves were estimated using a two-level linear regression model with cubic splines. All participants were divided into two groups: the northern group ( n = 5829) and the southern group ( n = 3246) based on the geographical division of China and male fetus group ( n = 4775) and female fetus group ( n = 4300) based on fetal gender. The EFW was compared by fetal gender and geographical group. All statistical models were adjusted for maternal sociodemographic characteristics. Results::A total of 9075 participants with 31,700 ultrasound measurement records were included in this study. Male fetuses demonstrated significantly larger EFW compared to female ones starting at 16 weeks of gestation and extending to delivery (global test P < 0.01). The overall geographic difference in EFW was significant (global test P = 0.03), and week-specific comparisons showed that the northern group had a greater EFW starting at 15 weeks of gestation and extending to 29 weeks of gestation, although this difference did not extend to the time of delivery. The Z-score of EFW confirmed that our Chinese fetal growth charts differed from previously published standards. Conclusion::This study provides EFW and ultrasound biometric reference measurements for Chinese fetuses and reveals differences from other fetal growth charts. The chart is worth promoting in more regions of China but should be tested prudently before use.

Objective::To build a reference fetal growth chart for the Chinese population based on fetal ultrasound measurements.Methods::This was a multicenter, population-based retrospective cohort study. Longitudinal ultrasound measurement data were collected from 24 hospitals in 18 provinces of China from 1 st September through 31 st October of 2019. The estimated fetal weight (EFW) was calculated based on head circumference, abdominal circumference, and femur length using Hadlock formula 3. Fetal growth curves were estimated using a two-level linear regression model with cubic splines. All participants were divided into two groups: the northern group ( n = 5829) and the southern group ( n = 3246) based on the geographical division of China and male fetus group ( n = 4775) and female fetus group ( n = 4300) based on fetal gender. The EFW was compared by fetal gender and geographical group. All statistical models were adjusted for maternal sociodemographic characteristics. Results::A total of 9075 participants with 31,700 ultrasound measurement records were included in this study. Male fetuses demonstrated significantly larger EFW compared to female ones starting at 16 weeks of gestation and extending to delivery (global test P < 0.01). The overall geographic difference in EFW was significant (global test P = 0.03), and week-specific comparisons showed that the northern group had a greater EFW starting at 15 weeks of gestation and extending to 29 weeks of gestation, although this difference did not extend to the time of delivery. The Z-score of EFW confirmed that our Chinese fetal growth charts differed from previously published standards. Conclusion::This study provides EFW and ultrasound biometric reference measurements for Chinese fetuses and reveals differences from other fetal growth charts. The chart is worth promoting in more regions of China but should be tested prudently before use.

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.