OP13.02: First trimester cervical angles for the prediction of spontaneous preterm birth

First trimester uterocervical angles for predicting spontaneous preterm birth (sPTB) in East Asian singleton pregnancies. We obtained transvaginal ultrasound images of the sagittal view of the cervix, including the anterior and posterior walls of the anteverted uterus from two groups of patients. The first group consisted of 3,504 cases with term births, while the second group consisted of 154 cases with sPTB < 37 weeks. Among the second group, there were 19 case with sPTB at < 34 weeks. Cervical length (CL) was measured. Angles between the endocervical canal, isthmus, anterior and posterior walls of uterus were determined as below: angle-A: two lines crossing the greatest curvature of cervix; angle-B: isthmus and endocervical canal; angle-C1: anterior wall and cervix including isthmus; angle-C2: anterior wall and endocervical canal; angle-D1: posterior wall and cervix including isthmus; angle-D2: posterior wall and endocervical canal; angle-E: anterior wall and isthmus; angle-F: posterior wall and isthmus. Uterocervical angles were expressed as multiples of the expected median (MoM) after adjusting for significant maternal and pregnancy characteristics. Bivariate correlation was performed between angles and CL. Models for predicting sPTB < 34 weeks and sPTB < 37 weeks using maternal factors (MF) and angles were assessed by AUC and sensitivity at fixed 10% false positive rate (FPR). All the cervical angles correlated with CL except angle-F. Relative to term birth, only median angle-E MoM was significantly increased in sPTB < 34 weeks whilst angle-D2 MoM was significantly reduced in sPTB < 37weeks. Angle-E MoM predicted 30% of sPTB < 34 weeks for a 10% FPR with AUC of 0.73 (95%CI: 0.71-0.75, p < 0.05). Difference in AUC when screening for sPTB < 37 weeks using MF+angle-D2 vs angle-D2 alone was not significant (AUC 0.57 vs 0.56; p > 0.05). First trimester uterocervical angles were not associated with an increased risk of sPTB except for angle-D2 and angle-E. Further prospective studies are needed to further determine prospective performance.