Insulin-like growth factor binding protein 1, Bishop score, and sonographic cervical length: tolerability and prediction of vaginal birth and vaginal birth within 24 hours following labour induction in nulliparous women

Abstract

To evaluate the tolerability of cervical insulin-like growth factor binding protein 1 (IGFBP-1) and its value as a predictor of successful labour induction, compared with Bishop score and transvaginal ultrasound (TVUS) cervical length. A prospective study. A tertiary hospital in Malaysia. A cohort of 193 term nulliparous women with intact membranes. Prior to labour induction, cervical fluid was obtained via a vaginal speculum and tested for IGFBP-1, followed by TVUS and finally Bishop score. After each assessment the procedure-related pain was scored from 0 to 10. Cut-off values for Bishop score and cervical length were obtained from the receiver operating characteristic (ROC) curve. Multivariable logistic regression analysis was performed. Vaginal delivery and vaginal delivery within 24 hours of starting induction. Bedside IGFBP-1 testing is better tolerated than Bishop score, but is less well tolerated than TVUS [median (interquartile range) of pain scores: 5 (4-5) versus 6 (5-7) versus 3 (2-3), respectively; P < 0.001]. IGFBP-1 independently predicted vaginal delivery (adjusted odds ratio, AOR 5.5; 95% confidence interval, 95% CI 2.3-12.9) and vaginal delivery within 24 hours of induction (AOR 4.9; 95% CI 2.1-11.6) after controlling for Bishop score (≥4 or ≥5), cervical length (≤29 or ≤27 mm), and other significant characteristics for which the Bishop score and TVUS were not predictive of vaginal delivery after adjustment. IGFBP-1 has 81% sensitivity, 59% specificity, positive and negative predictive values of 82 and 58%, respectively, and positive and negative likelihood ratios of 2.0 and 0.3 for vaginal delivery, respectively. IGFBP-1 better predicted vaginal delivery than BS or TVUS, and may help guide decision making regarding labour induction in nulliparous women. IGFBP-1: a stronger independent predictor of labour induction success than Bishop score or cervical sonography.