Estimation of the cervical length is a transvaginal ultrasound examination performed mainly during the anomaly scan. It is recommended for all pregnant women for their cervical length to be assessed. Women with history of multiple pregnancies, preterm labor, vaginal bleeding, evaluation of placenta position, surgery on the uterus or the cervix, congenital uterine abnormalities are advised to have this scan.

In high-risk women, depending on each case, there may be ongoing rescans every 2-4 weeks from the 15-17th week of pregnancy.