Relationship between detection of the cervical gland area during the late third trimester and necessity for induction of labor to prevent post-term delivery.

Abstract

With the maturation of the cervical canal during pregnancy, the cervical gland area (CGA) as observed on transvaginal ultrasonography is gradually obscured. The aim of this study was to elucidate the significance of CGA in the late third trimester as a determinant of the outcome of labor. We investigated 123 primiparous women with singleton pregnancies at 36-41weeks' gestation. The women were divided into two groups: a normal delivery group (93 women), which had vaginal delivery without medical intervention, and an induction of labor group (30 women), which required induction of labor after 41weeks and 0day. At outpatient prenatal checkups, the Bishop score (BS) was assessed by pelvic examination, and cervical length (CL) and CGA were evaluated by transvaginal ultrasonography. The relationship between each parameter and induction of labor was retrospectively determined and compared. Time-dependent assessment of each outcome determinant showed that the CGA detection rate was higher and the CL was longer in the induction of labor group from 3weeks to 1week before delivery at a significant level (P<0.05); however, the BS was significantly lower in the induction of labor group only at 1week before delivery (P<0.05). When multiple logistic regression analysis of the necessity of induction of labor was conducted using BS, CL, and CGA parameters as explanatory variables at 1week before delivery, CGA alone was shown to be an independent predictor of induction of labor (OR=6.1, 95% CI 2.3-16.2). The present study suggests that in the late third trimester, evaluation of CGA with transvaginal ultrasonography is most useful in predicting the necessity of induction of labor to prevent post-term delivery.