Object: To assess whether transvaginal ultrasound is helpful in predicting the post-term onset of labor (> or = 1 weeks).
Setting: Antenatal clinic of a University hospital and referral center. SUBJECT AND MEHODS: One hundred and twenty singleton uncomplicated pregnancies in primiparous women were enrolled at 37 weeks of gestation. Ultrasound examination of the cervical length by a transvaginal probe was performed at recruitment and at weekly intervals until 40 completed weeks. Subjects were divided into Group A (those with spontaneous onset of labor < or = 1 completed weeks) and Group B (those not in labor by that date).
Results: Eighty women delivered < or = 41 completed weeks, forty were not in labor by that date. The cervix was significantly shorter at 39 and 40 weeks in group A, but no particular cervical length was predictive of post-term delivery.
Discussion: There is a significant difference in cervical length in women delivering at term compared with those due to have a post-term delivery. This difference is significant from 39 weeks of gestation onwards. We speculate that targeted transvaginal ultrasound may be useful in predicting the post-term onset of labor and possibly in assisting its active management.