Abstract
<title>Abstract</title> <p>Background Vaginal examination (VE) is the reference method for monitoring labor, but it is subjective, operator-dependent, uncomfortable, and carries an infectious risk. Transperineal ultrasound (TPU) offers a non-invasive alternative. The aim of this study was to describe ultrasound aspects of labor parameters, compare them with clinical examination, and propose a “sonopartogram”. Methods This prospective, double-blind, comparative study was conducted over 5 months (February–June 2025) at Nabeul regional Hospital, Tunisia. We included 85 women with singleton pregnancy, cephalic presentation, term ≥ 37 weeks, and early labor. Before each routine VE, a TPU was performed to measure cervical length (CL), cervical dilatation (CD), head-perineum distance (HPD), posterior cervical angle (PCA), and fetal head position. Agreement was analysed by Bland-Altman, correlation by Pearson’s R, and qualitative concordance by Cohen’s kappa. Results Among the 85 women, ultrasound images were obtainable in 100% of cases for CL, CD, and HPD. For CL, good agreement was found (bias − 0.05 cm; R = 0.7). For CD during the active phase, the anteroposterior diameter showed excellent correlation (R = 0.93; bias 0.07 cm). For HPD, concordance was satisfactory, especially during the active phase. Fetal head position was poorly determined by VE (failure rate 86%, error 36%), while transabdominal ultrasound was the best method. A two-phase sonopartogram (latent and active) was developed. Conclusion Transperineal ultrasound is reliable, reproducible, and non-invasive for monitoring the first stage of labor. The proposed sonopartogram could become a valuable tool in Tunisian maternity units.</p>