Utility of the Simplified Bishop Score in Spontaneous Labor

Objective The objective of this study was to evaluate the relationship between the simplified Bishop score (SBS) on admission for labor and subsequent labor outcomes to identify women at higher risk for cesareans. Study Design This was a secondary analysis of a prospective cohort study of 4,733 singleton pregnancies. Adjusted odds ratios (aOR) were calculated comparing outcomes in women with an unfavorable SBS ≤ 5 to women with a favorable SBS > 5. A favorable SBS was compared with the individual parameters of dilation, effacement, and station. The primary outcome was vaginal delivery. Secondary outcomes were prolonged first stage, completion of first stage, oxytocin augmentation, and prolonged second stage. Results 47.8% of the patients admitted in labor had an unfavorable SBS. Nulliparous and multiparous patients with a favorable SBS were more likely to have a vaginal delivery (aOR 1.96, 95% confidence intervals [CI] 1.49-2.57; aOR 1.91, 95% CI 1.44-2.53) and less likely to require oxytocin augmentation (aOR 0.34, 95% CI 0.28-0.42; aOR 0.26, 95% CI 0.22-0.30. Compared with dilation alone, the SBS in its entirety was associated with a higher likelihood of vaginal delivery in nulliparous. Conclusion An unfavorable SBS on admission for labor is associated with a decreased likelihood of having a vaginal delivery.