Prediction Model for Successful Induction of Labor by Fetal Middle Cerebral Artery Pulsatility Index and Obstetric Factors in Term Pregnancy: A Prospective Cohort Study.

Abstract

Objective: Our study aimed to examine ultrasound and obstetric parameters, explore their interrelationships, and assess their predictive ability in determining the success of labor induction. Methodology: Women with uncomplicated singleton pregnancy at a gestational age of 40 weeks and 3 days with fetal cephalic presentation, having intact fetal membranes and unfavorable Bishop score (BS < 6) were recruited for the study. Ultrasound examination was performed to measure cervical length (CL), estimated fetal weight (EFW), and Doppler velocimetry of fetal cerebral vessels in each patient before induction. We proposed to combine the variables of CL, EFW, BS, and middle cerebral artery pulsatility index (MCA PI) to devise a model for the prediction of successful induction of labor (IOL). IOL was performed with intracervical prostaglandin E2 gel (3 g gel/0.5 mg dinoprostone) applied 6 h apart if needed, not more than 2 doses, followed by oxytocin infusion for up to 6 h. Successful induction was defined as the initiation of active labor at any stage of the induction process. Results: Among the 70 enrolled women, only 29 (41.4%) women responded to induction. CL, BS, and mean value of fetal MCA PI had significant differences in women who responded from those who did not respond to the IOL. The prediction model for the success of induction with the four variables of MCA PI, BS, and CL has a sensitivity of 100% and specificity of 90.2% (AUC 0.982, 95% CI: 0.96-1.00, p < 0.001) with the upper cutoff of 0.47. EFW showed to have no effect on the outcome parameter. Conclusion: A model comprising MCA PI, CL, and BS has an excellent prediction value to assess the response to IOL in women at term pregnancy. When a single parameter has to be evaluated, CL is the best maternal factor to predict the success of induction.