1034: Abdominal vs. vaginal approach for the mid-trimester cervical length screening

Abstract

Cervical length (CL) of less than 25mm is a risk factor for preterm birth. Recent studies have suggested the use of a routine cervical length (CL) measurement, to identify women at risk for preterm birth. In this study, we compared between transabdominal and transvaginal CL measurement in order to establish practical recommendations for CL screening following routine mid-trimester anatomy scan. CL measurements were performed at 20-24 weeks' gestation, from January 2017 until April 2018, immediately after fetal anatomy scan. CL measurements were obtained transabdominally before (full bladder), and transvaginally after (empty bladder) voiding. The differences in CL and duration of transabdominal and transvaginal measurements were compared between the groups and adjustment was made for maternal age (MA), and body mass index (BMI). 468 women carrying a singleton pregnancy gave their informed consent to participate in the study. The overall duration for the fetal anatomy scan was 27±5.3minutes. The duration of CL measured transabdominally was significantly shorter than the duration of CL measured transvaginally (6.9±1.38min vs. 0.46±0.3min, P<0.001). Difficulty in demonstrating the cervix transabdominally has been noted in 39 women (8.3%). The CL measured transvaginally was significantly longer than the CL measured transabdominally (42±7.5mm vs 37.34±6.8mm, p<0.001). The differences between the groups were unrelated to maternal age or BMI. All women whom transabdominal measurements of CL were above 35mm (66% of patients) had transvaginal CL above 25mm (98.2% of patient) (Fig 1). Transvaginal measurement of CL is associated with discomfort and embarrassment. Additionally, the transvaginal measurement is a time-consuming procedure with a significant prolongation of fetal anatomy scan compared with the transabdominal approach. Therefore, transabdominal measurement of CL should be offered as an initial tool for cervical length screening. Transvaginal measurements of CL should be reserved for high-risk women (who had preterm delivery in the past), when there are difficulties in demonstrating the cervix abdominally, and for women with transabdominal measurements of less than 35mm.