Objective: Characterize the incidence and timing of fetal heart rate (FHR) and cardiotocographic abnormalities (CTG) associated with the misoprostol vaginal insert (MVI) during labor induction.
Methods: This secondary analysis of data from the MVI Trial, a multi-site, double-masked, randomized trial of 374 women assigned to MVI 100, 150 or 200 mcg requiring cervical ripening before labor induction evaluated the incidence and clinical outcomes associated with FHR and CTG abnormalities diagnosed using 1997 NICHD definitions.
Results: MVI 200 was associated with an increased rate of tachysystole versus MVI 100 (p < 0.001, RR 2.11, 95% CI 1.39, 3.22) but not MVI 150 (p = 0.29, RR 1.31, 95% CI 0.82, 2.11). Tachysystole occurred with the drug in situ in 17 (14.4%) and 50 (38.2%) of MVI 100 and 200 subjects, respectively (p < 0.001). Category II or III FHR patterns after tachysystole occurred in 9 (7.6%) and 26 (19.8%) women in MVI 100 and 200 groups, (p = 0.006). Abnormal FHR patterns were the indication for cesarean in 18 (13.7%) MVI 200 women versus 11 (9.3%) MVI 100 women (p = 0.33). Neonatal outcomes were similar between groups.
Conclusions: While FHR and CTG abnormalities were encountered frequently during all inductions, few were clinically significant.