Transabdominal and transvaginal ultrasound assessment of cervical length - can transvaginal approach be avoided?

This study aimed to compare transabdominal (TA) and transvaginal (TV) ultrasound assessment of cervical length during pregnancy and to establish cervical length above which transvaginal measurement is not necessary.

Cervical length was measured using TA and TV method in the first (11 + 0-13 + 6 weeks), the second (20 + 0-21 + 6 weeks) and the third trimester (28 + 0-31 + 6 weeks) in 250 women with singleton pregnancy and low risk for preterm birth.

If the cervical length measured in the second trimester of pregnancy with transabdominal approach is ≥ 28.5 mm and ≥ 30.5 mm in the third trimester, it can be assumed with 100% sensitivity the cervical length measured with transvaginal method will be > 25 mm. Transabdominal cervical length measurement in the second and third trimester allows 89% and 65% of patients, respectively, to avoid transvaginal scan.

Second and third trimester screening by transabdominal cervical length measurements in a group of pregnant women with low risk for preterm birth is useful to determine which patients require transvaginal measurement.