The study group will be constituted by pregnant women in whom the operative delivery will be preceded by a transabdominal and transperineal ultrasound to evaluate fetal head position and fetal head station, by means of determination of the 'angle of progression'.

The control group will be constituted by pregnant women in whom the operative delivery will be carried out based solely on clinical criteria, namely transvaginal digital examination.

Transabdominal ultrasound, for determining fetal head position, is performed with the pregnant women in supine position after bladder emptying, with the transducer placed transversely on the suprapubic region of the maternal abdomen. For the sonographic determination of the fetal descent we will perform a transperineal ultrasound achieved by placing the ultrasound transducer on the perineum in a mid sagittal position between the labia below the pubic symphysis.

Severe postpartum hemorrhage, perineal trauma, prolonged hospital stay

low 5-minute Apgar score, umbilical artery metabolic acidosis, birth trauma and neonatal intensive care unit admission