Cervical length is the distance from the internal cervical os, the opening of the cervix into the uterus, to the external cervical os, the opening of the cervix into the vagina. This measurement is performed using transvaginal ultrasound and is most accurate when the bladder is empty, the probe is positioned without applying excessive pressure, and the measurement is taken along the endocervical canal. A normal cervical length in the second trimester is typically greater than 30 millimeters. Shorter measurements are associated with increased risk of preterm birth, and cervical length screening has become a routine part of prenatal care in many practices, particularly for women with risk factors for preterm delivery.
Sonography Term