Validation of Ultrasound "Angle of Progression" Measurement to Decrease the Cesarean Rate

Number of complicated deliveries in each group

A complicated deliveries is defined by the occurrence of at least one of the following events : * Failed instrumental extraction * Sequential use of a second instrument, * Difficult instrumental extraction defined as : * vacuum detachment * requires the use of a second instrument, * extraction time \> 10 minutes, * operator's impression of the difficulty of extraction, * Shoulder dystocia by obstetric maneuver

Time frame: baseline

Severe maternal morbidity, in each group

Severe maternal morbidity is defined by the occurrence of at least one of the following events: * postpartum hemorrhage requiring hysterectomy, embolization, conservative surgical treatment or blood transfusion, * third or fourth degree perineal tears * vaginal thrombus, * cervical tear, * surgical wounds * sepsis, amniotic embolism, cardiac complication or renal failure.

Time frame: 1 month

Severe neonatal morbidity, in each group

Severe neonatal morbidity, in each group, defined by the occurrence of at least one event below: * severe biological signs * moderate or absent biological signs but associated with perinatal events * seizure * severe neonatal trauma * Fetal death or neonatal death.

Time frame: 1 month

Rate of admission to neonatal intensive care unit, in each group

Number of newborns admitted to intensive care out of the total number of newborns

Time frame: 1 month

Concordance rate between the routinely AOP measurement and the centralized AOP measurement reading

Centralized blind AOP measurement reading

Time frame: 1 month