P01.01: Transabdominal cervical length measurements above 35mm exclude short cervix in both twin and singleton pregnancies

Abstract

To evaluate the discrepancies between transabdominal and transvaginal sonographic measurements of the cervix in singleton and twin pregnancies and to assess whether maternal weight influences these discrepancies. A prospective cohort study. Transabdominal and transvaginal cervical lengths measurements were obtained before and after voiding (respectively) in pregnant women between 14 and 25 weeks of gestation. Measurements were compared between singleton and twin pregnancies and correlated with maternal age, and BMI. Statistical analysis was performed in order to determine a transabdominal cervical length cut-off with 100% confidence for transvaginal cervical length above 30mm. 52 pairs of twin pregnancies and 388 singleton pregnancies were included. The mean cervical length measured abdominally for twin and singleton pregnancies was 35.6 ± 5.3mm and 36.8 ± 6.9mm respectively. The mean cervical length measured vaginally was 40.3 ± 6.6mm and 42.2 ± 7.2mm. The average discrepancy between the two methods was 4.7mm in twin pregnancies and 5.4mm in singleton. Abdominal cervix measurements correlated with vaginal measurements and were consistently shorter. The discrepancy between abdominal and vaginal measurements did not correlate with singleton or twin pregnancies, maternal body mass index or maternal age. All women with abdominal cervical length >35mm had a corresponding vaginal cervical length >30mm. The use of abdominal measurement of cervical length could be an effective initial tool for cervical length screening in both singleton and twin pregnancies. Cervical length of >35mm could be used as a cut-off value that might make the vaginal measurement redundant in some cases.