Studies on the Relationship between Cervical Ripening in the Third Trimester and Progress in Labor by a Prospective Registration Method. Part 3: Prediction of Onset of Labor and Its Outcome with the Bishop Score Obtained at Term

We carried out a prospective survey to clarify the relationships between the Bishop score at term and the clinical outcome of pregnancy. Data on the duration of gestation, duration of labor, mode of delivery, meconium staining, and Apgar score were described in our 1st report ( Acta Obstet Gynaecol Jap 2000; 52: 613–622). It was also demonstrated in our 2nd report ( Acta Obstet Gynaecol Jap 2001; 53: 1809–1818) that close correlations were observed between these factors and the Bishop score at term. This study investigated whether the Bishop score at term can be applied to predict labor onset, prolonged labor and pathological deliveries. The cases were classified according to the Bishop score at 37, 38 and 39 weeks of gestation. The total number of cases and that of cases delivered within a week after examinations were calculated for each Bishop score. The number of cases of deliveries at 41 weeks or later, prolonged labor (defined as 24 hours or more for primipara and 12 hours or more for multipara), operative or instrumental deliveries, meconium stainings and neonates with an Apgar score of 7 or less at 1 minute after birth were also counted for each Bishop score. Based on these figures, predictive values for every Bishop score as a criterion to predict each event described above were determined. The main Bishop score was then decided with the receiver‐operating characteristic curve as a criterion which yields the most reasonable combination of sensitivity and specificity for the prediction. It was also estimated if the score would result in statistical differences in the incidence of the events. In both primipara and multipara, more than half of the cases which had a Bishop score of 6 or more delivered within a week after the last examination regardless of the gestational week. Considering sensitivity for the prediction, 4 or more for primipara and 5 or more for multipara seemed useful values. It was also demonstrated that a Bishop score of 3 or less at 37 weeks of gestation, 3 or less at 38 and 5 or less at 39 for both primipara and multipara were applicable for predicting delivery at 41 weeks or later, a Bishop score of 2 or less at 37 weeks of gestation, 2 or less at 38 and 4 or less at 39 weeks of gestation for primipara, and 2 or less at 37 and 1 or less at 38 weeks of gestation for multipara for predicting prolonged labor, and a Bishop score of 2 or less at 37 weeks of gestation, 1 or less at 38 and 2 or less at 39 weeks of gestation for primipara, and 3 or less at 37, 38 and 39 weeks of gestation for multipara for predicting meconium staining. The Bishop score at term seemed inapplicable to the prediction of operative or instrumental deliveries and that of a low Apgar score. These results suggest that the Bishop score at term is valuable in predicting onset of labor, prolonged labor and the occurrence of meconium stained amniotic fluid. ACTA OBST GYNAEC JPN Vol. 54, No. 7, pp. 925–934, 2002