Decision-Making in Labor Admission Using Transperineal Ultrasound vs. Vaginal Examination

This single-center, prospective, randomized controlled clinical trial is designed to evaluate whether transperineal ultrasound provides a more effective and less discomforting method than standard vaginal examination for decision-making regarding hospital admission in term pregnant women presenting with contractions. Vaginal examination remains the standard approach for assessing labor progression but is known to be subjective, poorly reproducible, and frequently uncomfortable for patients. In contrast, transperineal ultrasound offers objective and reproducible parameters such as cervical dilation, fetal head station, angle of progression, and head-perineum distance. Incorporating these measurements into the clinical evaluation may optimize admission criteria, reduce unnecessary hospitalizations, and lower the rate of labor inductions. After obtaining informed consent, eligible participants will be randomly assigned in a 1:1 ratio to either a transperineal ultrasound group or a standard vaginal examination group. In the ultrasound group, hospital admission will be recommended when cervical dilation is ≥3 cm or the angle of progression exceeds 120°, in the presence of regular uterine contractions. In the vaginal examination group, admission will be recommended when cervical dilation is ≥4 cm with regular contractions. Maternal discomfort during the evaluation will be assessed on a 0-10 numerical scale, and all labor outcomes and interventions will be recorded in standardized case report forms. A total of 170 participants (85 per group) will be enrolled to detect an 18% difference in labor induction rates with 80% power and a 95% confidence level. Statistical analyses will include descriptive and comparative methods (Chi-square, t-test, or non-parametric equivalents), with significance defined as p\<0.05. The study will adhere to the principles of the Declaration of Helsinki and comply with applicable data protection regulations, including the Spanish Ley Orgánica de Protección de Datos (Organic Law on Data Protection, LOPD) and the European General Data Protection Regulation (GDPR).All participants will provide written informed consent prior to inclusion, and all data will be anonymized. The protocol has received approval from the institutional ethics committee. This trial builds upon prior observational findings demonstrating high agreement between ultrasound-based and traditional methods for assessing labor progression. By generating high-level evidence, it aims to support the implementation of transperineal ultrasound in labor triage protocols, improving the accuracy of clinical decision-making, enhancing maternal comfort, and contributing to better obstetric outcomes.

• Use of Oxytocin for Labor Augmentation [Time frame: During labor (up to delivery)]
• Time from Admission to Delivery [Time frame: From hospital admission to time of delivery]
• Mode of Delivery (as recorded in the medical record) [Time frame: At birth]
• Number of Vaginal Examinations Performed [Time frame: From hospital admission for labor to delivery]