Timing of cesarean delivery for fetal heart rate abnormalities in hypertensive pregnancies induced with oral misoprostol or Foley catheter: Secondary analysis of a randomized clinical trial

Objective: The study aims to assess how oral misoprostol for cervical ripening affects the time of cesarean delivery (CD) for fetal heart rate (FHR) abnormalities in pre-eclampsia patients. Secondary goals include determining the role of uterine hyperstimulation, comparing misoprostol with Foley catheter, and identifying risk factors for FHR abnormalities associated with CD.

Methods: A previously published randomized clinical trial was subjected to a secondary analysis (NCT01801410). We conducted a time-dependent analysis, stratifying the population based on the final mode of induction used (low-dose oral misoprostol vs Foley catheter).

Results: There was no CD for FHR abnormalities within 2 h of starting misoprostol. At 5 h, the cumulative incidence of CD for FHR abnormalities in the misoprostol group was 2.10%, while it was 1.00% in the Foley group (P = 0.565). After 25 h, the CD risk for FHR abnormalities remained constant in both groups at 21.00% (95% confidence interval [CI] 15.00%-28.00%). Within 5 h of misoprostol induction, the risk of uterine hyperstimulation was similar in both groups (0.33% in misoprostol vs 0.34% in Foley group, P = 0.161). The risk of CD for FHR abnormalities was unaffected by newborn weight centiles.

Conclusion: There was no significant difference in CD risk for FHR abnormalities between misoprostol and Foley catheter induction. Nonetheless, the cumulative incidence of CD for FHR abnormalities increased faster in the misoprostol group, indicating that FHR monitoring timing should be tailored to the induction method.