Bishop score and the outcome of labor induction with misoprostol

The aim of the study was to retrospectively identify possible factors for predicting the outcome of induction with misoprostol.

Fifty micrograms of misoprostol were administered intravaginally every 6 h during the first 2 days of induction, up to a maximum of 4 doses. The Bishop score, indication for induction, gestational length, maternal age, and parity were analyzed. The study involved 99 patients (47 primiparous and 52 multiparous) at term (>36 weeks of gestation) with unripe cervices.

Forty-five per cent of the patients achieved ripening of cervix and went into labor after a single dose of misoprostol; a further 45% required 2 doses. Nine patients received more than 2 tablets. Ninety-seven per cent of all vaginal deliveries occurred within the first 2 days of induction. Ninety-five per cent of the patients delivered vaginally when the Bishop score was >3, compared with 75% of those with a Bishop score of < or =3 (p=0.003). Among factors creating the Bishop scoring system, in logistic regression analysis effacement of the cervix was the only independent, significant predictor of cesarean section (p=0.003, OR = 0.16) even after adjusting for maternal age, which also was a significant predictor in the regression analysis. Eleven patients had previously had a cesarean section; one of them had a uterine rupture with a fatal outcome for the fetus. All women with a previously scarred uterus are now excluded from misoprostol treatment.

Misoprostol 50 microg administered intravaginally every 6 h according to this protocol is highly effective for inducing labor in carefully selected patients with unripe cervices.