Foley catheter (80 vs 60 mL) and misoprostol for labor induction in nulliparous women: a randomized controlled trial

Abstract

Background: Induction of labor is a common intervention in obstetrics worldwide. Foley catheter is a commonly used mechanical method for labor induction in nulliparous women with an unfavorable cervix at term. We hypothesize that a higher volume of Foley catheter (80 mL vs 60 mL) will shorten the induction-delivery interval for labor induction in nulliparous women at term with an unfavorable cervix with simultaneous use of vaginal misoprostol.

Objective: This study aimed to evaluate the effect of transcervical Foley catheter (80 mL vs 60 mL) with simultaneous use of vaginal misoprostol on the induction-delivery interval in nulliparous women at term with an unfavorable cervix for induction of labor.

Study design: In this double-blind, single-center, randomized controlled trial, nulliparous women with a term singleton gestation with unfavorable cervix were randomized to either group 1 (Foley catheter [80 mL] simultaneously with vaginal misoprostol 25 µg every 4h) or group 2 (Foley catheter [60 mL] with vaginal misoprostol 25 µg every 4h). The primary outcome was induction-delivery interval. Secondary outcomes were duration of the latent phase of labor, number of doses of vaginal misoprostol required, mode of delivery, as well as maternal and neonatal morbidity. Analyses were based on the intention-to-treat method. A sample size of 100 women per group (N=200) was selected.

Results: Between September 2021 to September 2022, 200 nulliparous women at term with an unfavorable cervix were randomized to labor induction with either FC (80 mL vs 60 mL) and vaginal misoprostol. Induction delivery interval (in minutes) was statistically significantly shorter in Foley catheter (80 mL) (median [interquartile range], 604 [524-719] vs 846 [596-990]; [P<.001]). Median time to labor onset (in minutes) (240 [120-300] vs 360 [180-600]; P<.001) was also shorter in group 1 (80 mL). The number of doses of misoprostol required for labor induction was statistically significantly less than with 80 mL (mean±standard deviation, 1.4±0.7 vs 2.4±1.3; P<.001). There was no statistically significant difference in the mode of delivery (vaginal delivery: 69 vs 80; odds ratio, 0.55 [1.1-0.3]; P=.104 and cesarean delivery: 29 vs 17; odds ratio, 0.99 [0.9-1.1]; P=.063, respectively). The relative risk of delivery within 12 hours with 80 mL was 2.4 [95% confidence interval, 1.68-3.43], P<.001. Maternal and neonatal morbidity were similar across the 2 groups.

Conclusion: FC (80 mL) simultaneously with vaginal misoprostol significantly shortens the induction-delivery interval (P<.001) in nulliparous women at term with an unfavorable cervix, as compared with Foley catheter 60 mL and vaginal misoprostol.

Keywords: Foley catheter; induction delivery interval; induction of labor; mechanical method; vaginal misoprostol.