Prevention of preterm birth based on short cervix: symptomatic women with preterm labor or premature prelabor rupture of membranes.

The diagnosis of preterm labor (PTL) is challenging, especially in women whose cervical dilatation is <2 cm and who are <80% effaced. In symptomatic women, with threatened PTL in both singletons and twins, transvaginal ultrasound cervical length (CL) identifies a high-risk group that is more likely to be in true PTL, more likely to deliver sooner, and more likely to deliver preterm. The addition of fetal fibronectin improves the predictive accuracy in women whose CL is <30 mm but >15 mm. Transvaginal ultrasound CL can also be performed in the presence of ruptured membranes and predicts latency. Although additional data are needed, the evidence so far suggests that the use of transvaginal ultrasound CL and fetal fibronectin can be used to better identify and manage women with PTL likely to have an imminent preterm delivery, and to avoid interventions in women who would not.