The Predicting Value of Ultrasonographic Measurement of Cervical Length and Internal os Dilatation in Preterm Delivery

Objective:To evaluate the predictive value of cervical length and internal os dilatation in preterm delivery in asymptomatic nulliparous women. Methods:We performed transvaginal ultrasonographic examination at 24～30 weeks' gestation in 600 nulliparous women with singleton fetus. We measured the length of uterine cervix and width of cervical internal os and followed up the pregnant outcome. Results:There were 38 spontaneous preterm births in 538 consecutive pregnant women.(7.1%). With the cervical length shorten, the risk of preterm delivery increased. According to ROC curve, 30mm or less of the cervieal length seemed to be the most suitable compromise. The sensitivity, the specificity,and positive predictive value was 15.8%,97.8%,and 37.5%,respectively.The relative risk (RR) of preterm delivery was 6.0. Dilatation to 5mm or more of internal os indicated 4.1-fold risk for preterm delivery.Conclusions:The transvaginal ultrasonographic examination of uterine cervix is an objective, effective, and repeatable method in predicting preterm delivery in asymptomatic nulliparous women.