The study aims to evaluate the effect of ultrasound-based visual feedback training of the pelvic floor muscles in nulliparous women at term pregnancy who present co-activation of the levator ani muscle, on the duration of the second stage of labor.

This is a single-center, no-profit, randomized controlled interventional study. Compared with standard clinical practice, patients will be enrolled at term pregnancy during routine antenatal care, when a first session of ultrasound-based visual feedback training will be performed using transperineal ultrasound.

Nulliparous women at term pregnancy showing co-activation of the levator ani muscle will be recruited within the standard care pathway. Participants will be randomized into two groups:

Group 1 (intervention): patients will undergo ultrasound-based visual feedback training, including real-time visualization on the ultrasound screen and explanation of the most appropriate pushing technique.

Group 2 (control): patients will receive only verbal instruction regarding the appropriate pushing technique.

Given the absence of known major confounding factors, simple randomization will be used. The randomization list will be generated electronically using the REDCap platform.

Recruitment will take place in the outpatient clinics of the Obstetrics and Prenatal Medicine Unit (U.O.C) at IRCCS AOU di Bologna, Sant'Orsola Hospital. Women in the intervention group will receive two ultrasound training sessions (visual feedback) one week apart at term pregnancy. Women in the control group, after enrollment, will be informed about the phenomenon of levator ani co-activation and will receive verbal instructions on how to relax the pelvic floor muscles.

After delivery, maternal and neonatal outcomes will be assessed, including mode of delivery, indication for operative vaginal delivery if applicable, duration of the second stage of labor, vaginal-perineal lacerations, other puerperal complications, neonatal arterial and venous pH, base excess (BE), birth weight, and neonatal intensive care unit (NICU) admission. Data will be collected through review of medical records at 40 days postpartum.

Inclusion Criteria:

• Nulliparous (first pregnancy)
• Adults (≥18 years old)
• Singleton pregnancy
• Presence of levator ani muscle co-activation at term pregnancy (37 weeks)
• Candidates for vaginal delivery
• Written informed consent signed for study participation

Exclusion Criteria:

• Presence of uterine malformations
• Presence of fetal malformations
• Presence of vaginal bleeding at the time of enrollment
• Regular uterine contractions
• Premature rupture of membranes