Induction of Labor with Oral Misoprostol - Effectiveness and Safety of Low-dose vs. High-dose Regimens

Before the market launch of low-dose misoprostol (LDM) in the form of 25 µg tablets, high-dose misoprostol (HDM) was used off-label for labor induction in Germany. The differences between the effectiveness and safety of both dosage forms were investigated.

This retrospective cohort study included all pregnant women who were induced with misoprostol between 2019 and 2023. Until September 2021, misoprostol was available in the form of a 200 µg tablet which was divided manually and administered orally at an initial dose of 50 µg, followed by 100 µg every four hours. This was compared with the current administration regimen of an initial dose of 25 µg followed by 50 µg in terms of vaginal birth rate, duration of induction, and maternal and neonatal outcomes.

A total of 1941 patients were analyzed; 1397 received HDM and 544 received LDM. Vaginal delivery was achieved with equal frequency (87% HDM vs. 88% LDM, p = 0.95). The duration of induction was shorter in the HDM group (20.7 hours vs. LDM 22.7 hours, p = 0.028), and opioid requirements were higher (HDM 74% vs. LDM 69%, p = 0.036). Maternal complications and neonatal outcomes did not differ. Regression analysis found that high BMI was an independent factor for a failed first induction attempt (B 0.002, SEM 0.0004, p < 0.001).

Both dosing regimens achieved high vaginal birth rates with comparable safety. Inductions with HDM were two hours shorter but were associated with higher opioid use.