Cervical length for prediction of preterm birth in women with multiple prior induced abortions.

OBJECTIVE: To determine whether transvaginal sonographic cervical length predicts preterm birth in women with multiple prior induced abortions. METHODS: This was a retrospective cohort study using the Thomas Jefferson University Prematurity Database. Patients with a singleton pregnancy and a history of more than one induced abortion were identified. Exclusion criteria were cerclage and indicated preterm birth. Subjects were followed with transvaginal ultrasound measurement of the cervix between 14 and 24 weeks' gestation and grouped into those with and those without a short cervix; a cervical length of < 25 mm was considered short. The primary outcome was spontaneous preterm birth at < 35 weeks. RESULTS: Fifteen of the 65 (23%) women with more than one induced abortion included in the study had a short cervix. The demographics and risk factors were similar between those with and those without a short cervix. The overall incidence of preterm birth was 21.5% (14/65); in women with a short cervix the incidence was 47% (7/15) and in women without a short cervix it was 14% (7/50). The sensitivity, specificity and positive and negative predictive values of a short cervix in the prediction of preterm birth were 50%, 84%, 47% and 86%, respectively. The relative risk of a short cervix for spontaneous preterm birth was 3.3 (95% CI, 1.4-7.4). CONCLUSION: A cervical length of < 25 mm on transvaginal ultrasound is predictive of preterm birth in women with more than one prior induced abortion. Women with multiple prior induced abortions and a short cervix have a 3.3-fold greater chance of spontaneous preterm birth compared with those with a cervical length of > or = 25mm.