The transperineal ultrasound (TPU) value of the angle of progression (AOP) during fetal head engagement, at station 0, is a critical cut-off for current obstetrical practice, especially when intrapartum instrumental interventions are required. Still, controversial measurements were reported in previous high resolution imagistic studies. Our TPU and direct “gold-standard” magnetic resonance (MRI) measurements confirm that station 0 corresponds to a 120° AOP, concordantly. Based on these findings, the fact that an AOP of 120° or greater was previously strongly associated with vaginal delivery may be due to the achievement of head engagement in labor.
Iliescu, D., Tudorache, S., Dragusin, R., Carbunaru, O., Patru, C., Florea, M., & Gheonea, I. A. (2015). The Angle of Progression at Station 0 and in Magnetic Resonance and Transperineal Ultrasound Assessment. Case Reports in Obstetrics and Gynecology, 2015, 1–3. https://doi.org/10.1155/2015/748327