Cervical insufficiency, previously called incompetent cervix, is a condition in which the cervix painlessly dilates and shortens during the second trimester of pregnancy, potentially leading to premature rupture of membranes and preterm delivery. Transvaginal ultrasound is the most accurate method for measuring cervical length, which is the key parameter used to screen for and monitor this condition. A cervical length of less than 25 millimeters before 24 weeks of gestation is generally considered short and increases the risk of preterm birth. Serial cervical length measurements help obstetricians decide whether interventions such as progesterone supplementation or cervical cerclage are needed to help maintain the pregnancy.
Sonography Term