Transvginal Sonography in the Prediction of Preterm Labor

Kim, Soo Pyung; Shin, Jong Chul; Kim, Chang Yee; Ryu, Jin Hee; Lee, Young; Choi, Eun Ah; Moon, Hee Bong; Kim, Ki Bum; Nam, Jung; Kwon, Soon Man

Abstract

OBJECTIVE
Preterm labor and delivery is probably the largest problem in modern perinatology. The early diagnosis of preterm labor is crucial for prevention of preterm birth. To predict the onset of preterm labor, we examined the diagnostic performance of serial cervical assessment by transvaginal sonography.
METHODS
In this prospective study, we performed transvaginal sonography at approximately 30 and 34 weeks of gestation in women with singleton pregnancies. Cervical parameters evaluated included endocervical length, the presence of funneling, funnel length and funnel width. We then assessed the relation between cervical parameters and the risk of spontaneous preterm labor.
RESULTS
We examined 258 women at approximately 30 weeks of gestation and 247 of these women again at approximately 34 weeks. Spontaneous preterm labor occurred in 9 of women examined at 30 weeks(Group 1) and in 13 at 34 weeks(Group 2). The endocervical length was normally distributed at 30 and 34 weeks(mean +/-SD, 38.26+/-6.82mm and 35.63+/-7.35mm, respectively). The endocervical length decreased significantly from 30weeks to 34 weeks(p=0.0001). Both groups showed significantly shorter endocervical length(p <0.05) and groupl more presence of funneling than group of term pregnancy(p<0.05). Receiver-operator characteristic curve and multiple logistic regression analyses indicated that endocervical length <-30mm at 30 weeks and <-25mm at 34 showed highest diagnostic index in predicting the onset of preterm labor(p=0.0001).
Conclusions
Serial transvaginal ultrasound assessment of endocervical length during early third trimester is a useful predictor of preterm labor and delivery in low-risk patients.