Digital and transvaginal ultrasound cervical assessment for prediction of successful labor induction.

Objective: To compare the values of preinduction transvaginal cervical length measurements and Bishop score to predict successful labor induction.

Methods: A prospective, observational trial of nulliparous women undergoing labor induction. Inclusion criteria were gestational age between 36 and 42 weeks, singleton cephalic presentation of the fetus, and intact membranes. Preinduction cervical ripening was performed using 25 microg intravaginal misoprostol (PGE1), repeated every 4 h, up to a maximum of 3 doses. Induction was subsequently continued by oxytocin and amniotomy.

Results: A total of 43 women met the inclusion criteria. Mean preinduction cervical length for women with successful or failed labor induction was 26 mm (95% Confidence interval [CI], 27-32) and 34 mm (95% CI, 33-38), respectively (P=0.002). Mean Bishop scores for successful and failed induction groups were 5.4 (95% CI, 5.2-6.2) and 3.1 (95% CI, 2.8-3.5), respectively (P=0.003).

Conclusion: Digital examination and transvaginal ultrasound of the cervix predict successful labor induction with reasonable accuracy.