This multicenter, prospective, randomized controlled trial will evaluate the efficacy and safety of bionic balloon-assisted delivery technology in nulliparous women planning vaginal delivery. Eligible participants will be randomly assigned in a 1:1 ratio to either the intervention group or the control group. Participants in the control group will receive routine labor management, while participants in the intervention group will receive bionic balloon-assisted delivery in addition to routine labor management after entering the active phase of labor.

The primary outcome is the duration of labor, including the first, second, and third stages of labor. Secondary outcomes include intrapartum cesarean conversion rate, intrapartum and postpartum complications, neonatal outcomes, postpartum pelvic floor dysfunction, postpartum depression, and maternal satisfaction. This study aims to determine whether bionic balloon-assisted delivery can shorten labor duration, reduce intrapartum cesarean conversion, and improve maternal and neonatal outcomes without increasing adverse events.

Bionic balloon-assisted delivery is a physical delivery-assistance technique designed to simulate the pressure and stimulation exerted by the fetal presenting part on the cervix and birth canal during labor. By providing controlled mechanical dilation of the upper and lower vagina during the active phase of labor, this technique may promote labor progress without the use of additional pharmacologic agents.

This study is a multicenter, prospective, randomized controlled trial designed to evaluate the efficacy and safety of bionic balloon-assisted delivery technology in nulliparous women planning vaginal delivery. Eligible participants will be women aged 18 to 45 years with singleton, term pregnancy, cephalic presentation, no contraindications to vaginal delivery, latent phase longer than 3 hours, cervical dilation greater than 4 to 5 centimeters indicating entry into the active phase of labor, fetal head engagement, and no obvious cephalopelvic disproportion. After written informed consent is obtained, participants will be randomly assigned in a 1:1 ratio to either the intervention group or the control group.

Participants in the control group will receive routine labor management for vaginal delivery. This includes close monitoring after the onset of labor, artificial rupture of membranes when cervical dilation reaches more than 4 to 5 centimeters and the fetal head is engaged, continued observation of uterine contractions, fetal heart rate, and amniotic fluid characteristics, and operative vaginal delivery or emergency cesarean section when clinically indicated.

Participants in the intervention group will receive bionic balloon-assisted delivery in addition to routine labor management. After the participant enters the active phase of labor and the fetal head is engaged, the KCB-II automatic bionic balloon-assisted delivery device will be used with a sterile latex balloon dilation handle. The balloon will be placed in the upper vagina near the fornix after artificial rupture of membranes and inflated according to the study protocol to mechanically dilate the birth canal. Other labor management procedures will follow routine clinical practice.

The primary outcome is the duration of labor, including the first, second, and third stages of labor. Secondary outcomes include intrapartum cesarean conversion rate; intrapartum and postpartum complications such as intrapartum fever, postpartum hemorrhage, postpartum infection, urinary retention, soft birth canal laceration, episiotomy, and operative vaginal delivery; neonatal outcomes including birth weight, Apgar scores, umbilical artery blood gas analysis results when available, neonatal complications, and admission to the neonatal intensive care unit; postpartum pelvic floor dysfunction; postpartum depression assessed using the Edinburgh Postnatal Depression Scale; and maternal satisfaction.

Participants will be followed through delivery, discharge, and the routine postpartum visit at 42 days after delivery. The study aims to determine whether bionic balloon-assisted delivery can shorten labor duration, reduce intrapartum cesarean conversion, and improve maternal and neonatal outcomes without increasing adverse events.

Inclusion Criteria:

• Age: 18-45 years;
• Nulliparous women with singleton, term pregnancy, cephalic presentation, and no contraindications to vaginal delivery;
• Latent phase longer than 3 hours, cervical dilation greater than 4-5 cm (entry into the active phase), fetal head engagement, and no obvious cephalopelvic disproportion;
• Voluntary participation in this study and signing of written informed consent.

Exclusion Criteria:

• Multiparous women;
• Non-cephalic presentation;
• Genital tract infection;
• High-risk pregnancy score classified as "red ball," "purple ball," or some "orange ball" categories, including severe medical or surgical comorbidities, placenta previa, scarred uterus, etc.;
• Presence of cephalopelvic disproportion, abnormal fetal heart rate, or other conditions unsuitable for vaginal delivery and requiring cesarean section;
• Other conditions considered unsuitable for enrollment by the clinician.

Individual participant data will not be shared publicly due to participant privacy and confidentiality considerations. De-identified aggregate results may be reported in scientific publications or presentations.

If there are other parties who are masked in the clinical trial besides those listed above, use this space to describe those parties.