Combined Misoprostol and Cervical Balloon vs Misoprostol Alone for Induction on the First Day in Primiparas

Primiparous Women

labor induction, misoprostol, foley balloon catheter

Misoprostol (a prostaglandin E1 analog) is commonly used for cervical ripening and labor induction via vaginal administration. The cervical balloon is another commonly used method that provides mechanical cervical dilation. Both methods are low-cost and widely available. Some meta-analyses have suggested that combined use may shorten the duration of labor, reduce the frequency of tachysystole, and lower NICU admission rates without increasing the risk of cesarean section. However, existing studies are heterogeneous and lack data from Asian populations. This study is being done to see whether combining two common methods of labor induction-misoprostol (a medicine placed in the vagina) and a cervical balloon (placed in the cervix) on the first day of induction-can shorten the time from the start of induction to delivery in first-time mothers during pregnancy . Participants will be randomly assigned to one of two groups: one group will receive misoprostol alone (standard care) on the first day of induction, and the other group will receive misoprostol plus a cervical balloon on the first day of induction. The main outcome measured is the time from the start of induction to delivery. The study will also look at safety outcomes, including the rate of cesarean section, maternal complications, and newborn outcomes.

This is a single-center, randomized, open-label, superiority randomized controlled trial. Participants will be randomly assigned in a 1:1 ratio to either the intervention group (misoprostol plus cervical balloon on the first day of induction) or the control group (misoprostol alone on the first day of induction). IPRIMARY OUTCOME: Time from initiation of labor induction to delivery (hours). SECONDARY OUTCOMES: Time from induction to amniotomy (min), time from induction to spontaneous membrane rupture (h), time from induction to onset of labor (min), duration of balloon use (min), duration of oxytocin use (min), duration of latent phase (h), duration of first and second stages of labor (min), mode of delivery, degree of perineal laceration, indications for forceps/episiotomy/cesarean section, fetal distress, intrauterine infection, neonatal outcomes (birth weight, Apgar score, umbilical artery pH/BE, NICU admission), and maternal hemoglobin difference before and after delivery. Safety outcomes include placental abruption, septic shock, and severe postpartum hemorrhage. SAMPLE SIZE: Based on historical data from 90 primiparous women at Peking University First Hospital (June 2025), the mean induction-to-delivery interval was 39.07 ± 19.92 hours. Assuming an 8-hour reduction in the intervention group, with a two-sided alpha of 0.05, power of 80%, and a 10% dropout rate, each group requires 110 participants (total 220). STATISTICAL ANALYSIS: Continuous variables will be compared using t-test or Mann-Whitney U test as appropriate. Categorical variables will be compared using chi-square or Fisher's exact test. Multivariable linear regression and logistic regression will be used for adjusted analyses. Subgroup analyses will be performed by type of hyperglycemia, age, BMI, and baseline Bishop score. ETHICS AND REGISTRATION: This study has been approved by the Biomedical Research Ethics Committee of Peking University First Hospital (Approval No. 2025R0393-0002, dated September 25, 2025). The study is registered on ClinicalTrials.gov. STUDY PERIOD: June 2026 to December 2026.

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