Distribution of uterocervical angles of pregnant women at 16+0 to 23+6 weeks gestation with low risk for preterm birth: first vietnamese cohort of women with singleton pregnancies

BackgroundCervical length (CL) measured by ultrasound in the second trimester is a predictor of spontaneous preterm birth (sPTB). The uterocervical angle (UCA) has recently been suggested as a predictor to identify women at risk of sPTB. The aim of this study was to investigate the UCAs' distribution in singleton pregnant women at 16(+ 0) - 23(+ 6) weeks of gestation with low risk for sPTB.MethodsThis was a prospective cohort study of 1,051 pregnant women with singleton pregnancies at low risk for preterm delivery. Pregnant women with a viable singleton fetus at 16(+ 0) - 23(+ 6) weeks of gestation were enrolled in the study conducted at the Haiphong Hospital of Obstetrics and Gynecology, Vietnam, from 09/2019 to 09/2020. CL and the UCA were assessed using transvaginal ultrasonography (TVS) by a single sonographer. Subjects were followed-up until the end of pregnancy, and maternal and neonatal outcomes were recorded. The UCAs' range and their relationship with gestational age were evaluated using regression analysis. P < 0.05 was considered statistically significant.ResultsThe normal range of the UCA (5(th) - 95(th) percentiles) was 46.47 degrees (95% CI, 40.27 degrees-51.81 degrees) to 127.06 degrees (95% CI, 123.02 degrees - 130.71 degrees). The UCAs in the preterm birth (< 37 weeks) and full-term groups were 117.86 degrees +/- 20.25 degrees and 83.80 degrees +/- 24.18 degrees, respectively (p < 0.001). Linear regression analysis showed a significant change in the UCA range from 16(+ 0) to 23(+ 6) weeks of gestation (2.51 degrees per week, p < 0.001). The linear function yielded the highest correlation coefficient in the variation rule of the UCA values (r = 0.22). A total of 42/63 (66.7%) patients with preterm birth < 37 weeks had a UCA above the 75(th) percentile. The majority of women with preterm birth had a UCA >= 95 degrees compared with those with full-term delivery (88.9% vs. 31.3%, p < 0.001).ConclusionsThe results of this study present background information about the normal range of UCA values in singleton pregnant women at 16(+ 0) to 23(+ 6) weeks at low risk for sPTB in this Vietnamese cohort. In this study population at low risk for sPTB, pregnant women with a UCA value >= 95(o) were also considered at risk for preterm birth.