The Bishop score as a determinant of labour induction success: a systematic review and meta-analysis

PURPOSE: To evaluate the association between the Bishop Score and successful induction. STUDY STRATEGY AND SELECTION CRITERIA: We searched the PubMed and the lists of references of relevant studies to identify reports on the association between Bishop Score and achieving active phase of labour or vaginal delivery. DATA COLLECTION AND ANALYSIS: We abstracted crude or adjusted measures of association from studies. Summary odds ratio (OR) and summary hazard ratio (HR), and 95 % confidence interval (95 % CI) were obtained by random effects meta-analysis. Study heterogeneity was assessed using the I (2) test. RESULTS: Fifty-nine studies met the inclusion criteria. Analyses with crude ORs showed that women with higher versus lower Bishop Score were more likely to achieve vaginal delivery either with no time limit for this to occur, or within a certain time interval; the summary ORs according to the Bishop Score cutoff ranged from 1.98 (95 % CI: 1.58-2.48; I (2) = 36.6 %) to 5.48 (95 % CI: 1.67-17.96; I (2) = 0.0 %) and from 2.15 (95 % CI: 1.36-3.40; I (2) = 0.0 %) to 4.22 (95 % CI: 2.48-7.17; I (2) = 11.0 %), respectively. Summary estimates per unit increase in the Bishop Score, based on adjusted ORs, showed a positive association with achieving vaginal delivery, either with no time limit (OR(summary) = 1.33; 95 % CI: 1.13-1.56; I (2) = 66.1 %) or within a certain time interval (OR(summary) = 1.52; 95 % CI: 1.37-1.70; I (2) = 42.4 %). Summary HRs per unit increase in Bishop Score showed an association with induction to vaginal delivery (HR(summary) = 1.28; 95 % CI: 1.21-1.36; I (2) = 0.0 %), but not with induction to active phase (HR(summary) = 1.21; 95 % CI: 0.88-1.68; I (2) = 70.7 %) time interval. CONCLUSIONS: Bishop Score seems be a determinant of achieving vaginal delivery and is associated with induction-to-vaginal delivery time interval