The Effect of Nipple Stimulation Combined With Foley Balloon Catheter on Bishop Score and Induction-to-delivery Interval: a Prospective Randomized Trial

Rates of labor induction have increased substantially in recent decades in Israel and worldwide. Cervical ripening is a critical component of successful labor induction, and an unfavorable cervix, as reflected by a low Bishop score, is associated with prolonged induction, increased need for additional interventions, and higher rates of operative delivery. Mechanical methods, particularly the Foley balloon catheter, are commonly used for cervical ripening due to their effectiveness and favorable safety profile, including a lower risk of uterine tachysystole compared with pharmacologic agents.

Nipple stimulation is a non-pharmacologic, physiologic method that promotes endogenous oxytocin release and uterine contractions, mimicking spontaneous labor. Prior studies have suggested that nipple stimulation may reduce the need for exogenous oxytocin and lower the incidence of uterine hyperstimulation, while achieving comparable maternal and neonatal outcomes. However, the combined use of nipple stimulation with mechanical cervical ripening has not been systematically evaluated.

This study is a prospective, randomized, double-blinded controlled trial designed to evaluate whether the addition of nipple stimulation to Foley balloon catheter cervical ripening improves cervical readiness and shortens the induction-to-delivery interval compared with Foley balloon catheter alone. Eligible participants are term pregnant patients (37-42 weeks' gestation) with singleton, cephalic pregnancies, intact membranes, and an unfavorable cervix (Bishop score <6) who require labor induction for standard obstetric indications.

Participants will be randomized in a 1:1 ratio to one of two study groups. The intervention group will undergo cervical ripening with a Foley balloon catheter in combination with a standardized nipple stimulation protocol using a breast pump. Nipple stimulation will begin one hour after catheter insertion and will consist of alternating stimulation of each breast for 15 minutes with 15-minute rest intervals, for up to six hours, at the maximum tolerable intensity. The control group will receive cervical ripening with a Foley balloon catheter alone, with standard obstetric management.

Fetal heart rate monitoring will be performed at regular intervals according to institutional protocols, with increased monitoring as clinically indicated. The balloon catheter will be removed after 12 hours, earlier if spontaneous labor ensues, membranes rupture, uterine tachysystole occurs, or non-reassuring fetal status is suspected.

Primary outcomes include the change in Bishop score following catheter removal and the induction-to-delivery interval. Secondary outcomes include the need for additional induction methods (e.g., oxytocin or prostaglandins), time to active labor, mode of delivery, maternal complications (including intrapartum fever, chorioamnionitis, postpartum hemorrhage, and uterine tachysystole), neonatal outcomes (Apgar scores, umbilical cord pH, NICU admission), maternal pain and satisfaction scores, and breastfeeding rates.

The findings of this study will provide evidence regarding the efficacy and safety of integrating a physiologic intervention with mechanical cervical ripening and may inform future strategies to optimize labor induction while minimizing pharmacologic exposure.