Pushing using real-time sonographic ultrasound education (PURSUE): A study protocol for a randomized controlled trial

INTRODUCTION: Maternal expulsive force is a key determinant of fetal head descent during the active second stage of labour. Pushing is most effective when abdominal muscle contraction is synchronised with relaxation of the levator ani muscle, thereby widening the pelvic hiatus. Trans-perineal ultrasound studies show that 15-20% of nulliparous women paradoxically contract the levator ani (co-activation) during pushing, narrowing the hiatus and slowing head descent. Consequently, about 20% of primigravidas experience a prolonged second stage, with higher rates of operative birth and perineal trauma. METHODS AND ANALYSIS: PURSUE is a single-centre, open-label, parallel-group RCT at Fondazione Policlinico A. Gemelli, Rome reported according to the SPIRIT 2013 and CONSORT 2010 guidelines. Nulliparous women between 28 + 0 and 37 + 0 weeks of gestation will be randomised 1:1 to midwife-led pushing training without ultrasound biofeedback or a midwife-led session combining theoretical instruction with real-time TPUS-guided pushing training. The primary endpoint is duration of the active second-stage of labour (minutes). Secondary outcomes include levator ani co-activation amplitude, spontaneous vaginal birth, perineal trauma, postpartum haemorrhage ≥ 500 mL, urinary/faecal incontinence at 6, 12 and 16 weeks postpartum and childbirth experience (CEQ-2). A sample of 228 (114 per arm) provides 80% power to detect a clinically meaningful reduction of 20 minutes(Cohen's d = 0.37; α = 0.05, two sided). Allowing for 15% attrition, 268 women will be enrolled. The primary analyses uses multivariate linear regression adjusting for pre-specified covariates; secondary analyses are exploratory. ETHICS AND DISSEMINATION: The protocol is approved by Lazio Region Ethics Committee (Prot. 0000641/25) and registered on ClinicalTrials.gov (NCT07000240). Written informed consent is obtained at enrolment. An internal independent committee oversees safety. No formal interim analysis with pre-specified stopping rules is planned; accordingly, no alpha-spending adjustment is applied, and the pre-specified primary (confirmatory) analysis will be performed once, on the complete sample, after the end of follow-up. During the trial, preliminary results may be presented at scientific meetings for reporting and feasibility purposes; such presentations are exploratory and non-confirmatory, are not used to inform any decision to stop or modify the trial, and do not affect the pre-specified primary analysis or the control of the type I error rate. Results, the anonymised dataset and statistical code will be disseminated through peer-reviewed journals, conference presentations and an open-access repository within 12 months of completion. TRIAL REGISTRATION: ClinicalTrials.gov NCT07000240.