Cardiotocographic abnormalities associated with misoprostol and dinoprostone cervical ripening and labor induction

To characterize the incidence and timing of cardiotocographic (CTG) abnormalities associated with misoprostol and dinoprostone vaginal inserts during labor induction.

This was a secondary analysis of data collected during the misoprostol vaginal insert (MVI) trial, a multi-site, double-masked, randomized trial of women requiring cervical ripening before induction of labor. The timing, incidence and clinical outcomes associated with CTG abnormalities were analyzed among three study groups.

1308 subjects were randomized to receive dinoprostone pessary, misoprostol 50 mcg (MVI 50) or 100 mcg (MVI 100) vaginal insert. 6.8% of MVI 50-treated women had a uterine contractile abnormality (hyperstimulation, hypertonus and/or tachysystole) while the study drug was in situ, compared to 17.4% with dinoprostone insert (p<0.001) and 17.3% with MVI 100 (p<0.001). There was no significant difference in incidence of fetal heart rate (FHR) abnormalities that occurred with the study drug-11.2% with dinoprostone, compared to 9.9% with MVI 50 and 10.7% with MVI 100. Cardiotocographic (CTG) abnormalities while the study drug was in situ occurred later in women treated with MVI 50 (7.5h [6.2-9.8]) compared to dinoprostone (5.5h [4.2-6.6], p=0.003) and MVI 100 (7.0 h [5.7-7.9], p=0.13). Eight participants in MVI 50 group underwent cesarean section secondary to a CTG event that was initially noted with the study drug in situ, compared to eight dinoprostone-treated participants and 16 in the MVI 100 group, but these differences were not statistically significant.

Cardiotocographic abnormalities were less frequent and occurred after longer exposure with MVI 50 than MVI 100 or dinoprostone. Clinical outcomes were similar among the groups.