The predictive value of the distance between the placenta and the internal os of the cervix in second trimester to placenta previa / 中国医师杂志

ABSTRACT

Objective:To explore the predictive value of the distance between the placenta and the internal os of the cervix (IOD) in second trimester to placenta previa.Methods:476 pregnant women with placenta previa diagnosed by systematic ultrasound in the Affiliated Hospital of North Sichuan Medical College from May 2016 to June 2020 were analyzed retrospectively. The ultrasonic parameters such as IOD, cervical length and placental main attachment position were measured, and the clinical characteristics and pregnancy outcome were recorded. Logistic regression analysis was used to analyze the influencing factors of placenta previa from mild pregnancy to late pregnancy. The receiver operating characteristic (ROC) curve was used to analyze the predictive value of IOD value for placenta previa.Results:197 cases of placenta previa were diagnosed in this study. Multivariate regression analysis showed that the number of previous pregnancies, IOD and history of cesarean section were the related factors of placenta previa from mid pregnancy to late pregnancy ( P<0.05). The risk of placenta previa in pregnant women ≥3 pregnancies was 1.826 times that in pregnant women with less than 3 pregnancies. The risk of placenta previa when the lower edge of placenta covers and crosses the internal orifice of cervix (IOD<0 mm) was 11.494 times that of IOD=0 mm and 22.222 times that of IOD>0 mm<20 mm (low placenta). The risk of placenta previa in pregnant women with a history of cesarean section was 1.908 times that of pregnant women without a history of cesarean section. When the cutoff value of IDO was 20 mm, all pregnant women with placenta previa could be screened out in the group with cesarean section history and the area under the curve (AUC) was 0.840 (95% CI 0.783-0.896, P<0.05); When the cutoff value of IOD was 13.5 mm, all pregnant women with placenta previa could be screened in the group without cesarean section history, and the AUC was 0.814 (95% CI 0.759-0.869, P<0.05). Conclusions:The second trimester IOD has a good predictive value for placenta previa.