Fetal heart rate patterns and the incidence of adverse events after oral misoprostol administration for cervical ripening among low-risk pregnancies

Abstract

Objective: Though misoprostol is commonly used for inpatient cervical ripening, its use in outpatient settings has been limited by safety concerns. This study was conducted to assess the association between early fetal heart tracing (FHT) and maternal tocodynamometry patterns and the incidence of adverse fetal and pregnancy outcomes after the administration of oral misoprostol for cervical ripening. Methods: We conducted a retrospective cohort study of 9908 low-risk patients at ≥37 weeks gestation who received oral misoprostol for cervical ripening prior to rupture of membranes between 01/01/2012 and 12/31/2017 at Kaiser Permanente Northern California hospitals as inpatients. We excluded patients who received a different agent for cervical ripening or had any need for additional inpatient monitoring, including hypertensive disorders of pregnancy, diabetes, or intrauterine growth restriction. Abnormal FHT, abnormal uterine activity, and adverse pregnancy or fetal-related events documented in the electronic health record in the four hours after administration of the first and second doses of misoprostol were assessed using descriptive statistics. Results: We found that 0.9% of patients experienced tachysystole after the first dose of misoprostol (0.6% without decelerations; 0.3% with decelerations). The incidence of variable decelerations only and other FHT abnormalities (i.e. bradycardia, late or prolonged decelerations, or absent or minimal variability) in the first hour after misoprostol administration were 7.1% and 6.7% respectively, and diminished over time. The need for tocolytic use was 0.2% in the first hour and declined over time to 0.03% in the fourth hour after the first dose. Urgent cesarean delivery occurred in 0.1% of patients after receiving the first dose of misoprostol. Patients who did not experience variable, prolonged, or late decelerations in the first hour after the initial misoprostol dose were less likely to have such FHT abnormalities in the subsequent three hours compared to patients who had other FHT abnormalities (11.8% among patients with no FHT abnormalities vs. 43.7% among patients with other FHT abnormalities; p