Predictors of newborn admission after labour induction at term: Bishop score, pre-induction ultrasonography and clinical risk factors.

INTRODUCTION: Following labour induction at term, 12 percent of neonates can expected to be admitted to the neonatal intensive care unit. We aimed to evaluate the Bishop score, pre-induction ultrasonography (US) assessment of amniotic fluid, foetal weight and cervical length, and pre-induction and intrapartum risk factors as predictors of neonatal admission.

METHODS: 152 women at term, scheduled for labour induction, consented to participate in this prospective study. Transabdominal US was performed to obtain foetal biometry and amniotic fluid index, followed by transvaginal US to measure cervical length. US findings were concealed. The Bishop score was obtained at initiation of labour induction. Pre-induction and intrapartum risk factors were also considered in the multivariate logistic regression analysis. All study women received standard care.

RESULTS: On univariate analysis, factors associated with neonatal admission were: gestational age at less than or equal to 40 weeks, labour induction for diabetes mellitus, Bishop score of less than 5 at initiation of labour induction, estimated foetal weight of less than 2.5 kg by US, induction to delivery interval of more than 24 hours, caesarean delivery and umbilical cord blood pH of less than 7.1. Cervical length of greater than 20 mm on transvaginal US (p-value is 0.10) was not significant. After multivariate logistic regression analysis, controlling for the significant variables, only the unfavourable Bishop score (adjusted OR 4.2; 95% CI 1.2-13.8; p-value is 0.02) and caesarean delivery (adjusted OR 3.9; 95% CI 1.1-13.7; p-value is 0.035) were independent predictors of neonatal admission.

CONCLUSION: The identification of an unfavourable Bishop score as an independent predictor of neonatal admission is useful in the counselling of women who are considering labour induction.