Sonographic measurement of cervical length in preterm prelabor amniorrhexis.

OBJECTIVE: To determine whether sonographic measurement of cervical length in pregnancies complicated by preterm prelabor amniorrhexis helps distinguish between those women who deliver within 7 days and those who do not. METHODS: In 101 women with singleton pregnancies presenting with preterm prelabor amniorrhexis at 24-36 (median, 32) weeks of gestation cervical length was measured by transvaginal ultrasound. Exclusion criteria were active labor defined by the presence of cervical dilatation of > or = 3 cm and iatrogenic delivery for fetal or maternal indication when not in active labor. The clinical management was determined by the attending obstetrician. The primary outcome of the study was delivery within 7 days of presentation. RESULTS: Delivery within 7 days of presentation occurred in 58/101 (57%) pregnancies. Logistic regression analysis demonstrated that significant independent contribution in the prediction of delivery within 7 days was provided by cervical length (odds ratio (OR) = 0.91, 95% CI 0.86-0.96, P = 0.001), gestation at presentation (OR = 1.35, 95% CI 1.14-1.59, P = 0.001) and presence of contractions at presentation (OR = 3.07, 95% CI 1.05-8.92, P = 0.039) with no significant independent contribution from ethnic origin, maternal age, body mass index, parity, previous history of preterm delivery, cigarette smoking, vaginal bleeding or the administration of tocolytics, antibiotics or steroids. CONCLUSION: In women with preterm prelabor amniorrhexis prediction of delivery within 7 days is provided by cervical length, gestation and presence of contractions at presentation.