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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
220
25 μg misoprostol tablet placed in the posterior vaginal fornix for cervical ripening and labor induction on the first day. May be repeated up to 3-4 times based on uterine contraction response (monitored every 2-4 hours).
A Cervical balloon with 80 mL sterile water inflation placed intracervically for mechanical cervical dilation. The balloon is left in place for up to 12-24 hours or until spontaneous expulsion.
Time from initiation of labor induction to delivery
Time in hours from the start of labor induction (placement of first dose of misoprostol or Foley balloon) to vaginal delivery or cesarean section.
Time frame: Time from initiation of induction measures on the first day of induction to delivery (control group: time of first misoprostol placement; intervention group: time of cervical balloon and misoprostol placement).
Time from Induction to Amniotomy
Duration from the start of induction (placement of misoprostol or balloon+misoprostol) to the performance of amniotomy, measured in minutes.
Time frame: From start of induction to amniotomy
Time from Induction to Spontaneous Membrane Rupture
Duration from the start of induction to spontaneous rupture of fetal membranes, measured in hours.
Time frame: From start of induction to spontaneous rupture
Time from Induction to Onset of Labor
Duration from the start of induction to the establishment of regular painful uterine contractions with cervical opening, measured in minutes.
Time frame: From start of induction to onset of labor
Duration of Balloon Use
Total time the cervical balloon remains in place (from insertion to removal), measured in minutes.
Time frame: From balloon insertion to removal, assessed during the induction period (up to 24 hours).
Duration of Oxytocin Use
Total duration of oxytocin administration during labor, measured in minutes.
Time frame: From start to stop of oxytocin infusion, assessed during labor
Duration of Latent Phase of Labor
Time from onset of labor to cervical dilation of 5 cm, measured in hours.
Time frame: From onset of labor to active phase, assessed during labor
Duration of First and Second Stages of Labor
Time from full cervical dilation (first stage) to delivery of the newborn (second stage), measured in minutes
Time frame: From full dilation to delivery, assessed during the second stage
Mode of Delivery
Categorization of delivery as spontaneous vaginal, vacuum/forceps-assisted, or cesarean section.
Time frame: At the time of delivery.
Degree of Perineal Laceration
Severity of perineal tears classified as first-, second-, third-, or fourth-degree.
Time frame: Immediately after vaginal delivery.
Indications for Forceps/Episiotomy/Cesarean Section
Clinical reasons for performing forceps delivery, episiotomy, or cesarean section (e.g., fetal distress, arrest of labor).
Time frame: At the time of the operative intervention (during labor/delivery).
Fetal Distress
Presence of fetal distress diagnosed by abnormal fetal heart rate patterns or acidemia during labor.
Time frame: During labor, assessed up to delivery.
Intrauterine Infection
Clinical or histologic diagnosis of chorioamnionitis or endometritis during or after delivery.
Time frame: During labor and up to 48 hours postpartum.
Neonatal Birth Weight
Weight of the newborn measured immediately after delivery, in grams.
Time frame: At delivery (immediately after birth).
Apgar Score
Apgar score assessed at 1 and 5 minutes after birth, range 0-10.
Time frame: At 1 and 5 minutes after birth.
Umbilical Artery pH and Base Excess
pH and base excess (BE) values measured in umbilical artery blood at delivery.
Time frame: Immediately after delivery (from cord blood).
NICU Admission
Whether the newborn is admitted to the NICU after delivery.
Time frame: After birth.
Maternal Hemoglobin Difference
Difference between pre-delivery (baseline) and post-delivery hemoglobin levels, measured in g/dL.
Time frame: Baseline (before induction) and within 24-48 hours after delivery.
Placental Abruption
Premature separation of the placenta from the uterine wall, diagnosed clinically or by ultrasound.
Time frame: During labor and delivery
Septic Shock
Severe infection leading to circulatory failure, requiring vasopressors.
Time frame: Before or after birth
Severe Postpartum Hemorrhage
Estimated blood loss ≥1000 mL or requiring transfusion or surgical intervention.
Time frame: Within 24 hours after delivery.
Jianhua Niu, M.D.
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