P279: Effects of preterm rupture of membrane on pregnancy outcome

Abstract

Objective: In threatened preterm labour less than 15% of the women will progress to active labour and delivery. This study investigates if cervical length measurements by transvaginal ultrasound can discriminate between true and false labour in women presenting with preterm contractions. Methods: Cervical length was measured by transvaginal ultrasound in 253 women with singleton pregnancies presenting with painful uterine contractions at 24–36 (median 30.5) weeks of gestation. Women presenting in active labour defined by cervical dilatation, with ruptured membranes and those that underwent prior or subsequent cervical cerclage were excluded from the study. The clinical management was determined by the attending obstetrician without taking into account the cervical length. Primary outcome of the study was delivery within seven days of presentation. Results: Delivery within seven days of presentation occurred in 21 of the 253 (8.2%) pregnancies and this was inversely related to cervical length. In 209 cases the cervical length was 15 mm or more and only two of these (1%) delivered within seven days. In the 44 with cervical length less than 15 mm delivery within seven days of presentation occurred in 19 (43.2%). Logistic regression analysis demonstrated that significant independent contribution in the prediction of delivery within seven days was provided by cervical length (p < 0.0001), previous contraction frequency at presentation (p < 0.009), history of preterm delivery (p < 0.01) and vaginal bleeding (p < 0.019) with no significant contribution from gestation at presentation, ethnic origin, maternal age, parity, cigarette smoking or the administration of tocolysis, antibiotics or steroids. Conclusions: Sonographic measurement of cervical length helps to avoid over-diagnosis of preterm labour in women with preterm contractions and intact membranes and may be helpful to avoid unnecessary intervention.