Failure of descent due to fetal malposition is one of the most common indications for performing surgical deliveries. It has recently been suggested that trans-perineal intra-partum ultrasonography may be useful in assessing fetal head engagement, position and station as well as it's reliable, cheap, painless and effective tool. Measuring the 'angle of progression' could assist in the obstetrician's decision regarding mode of delivery. Objectives: The primary outcome is to use the AOP to

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... a predictive model for the probability of successful vaginal delivery. Secondary outcomes including assessment of possibly successful VBAC in previous one CS women. Methods: We recruited 500 women in labor. For each woman, a (TPU) was performed to measure the AOP in late first and second stages of labor. We compared AOP between women who delivered fetuses through vaginal route to those who delivered by CS. Results: Through 467 women included in the study, AOP was significantly Higher in spontaneous vaginal delivery group (with cut off 123°±8.5°) as compared with women delivered by vacuum or by CS (113°±10.5°) (P=0.003). The VBAC as another secodary outcome seems to be insignificant. Conclusions: TPU is safe, non-invasive and easily preformed technique which is useful to predict labor outcomes.