The reduction in the rate of caesarean section is a major public health issue, it has reached 21% in 2010 Fance. Indeed complications to expect during pregnancy and childbirth increase doubles the risk of fetal morbidity, néonatal and maternal history of when césareinne. recommendations for clinical practice (RPC) to "scarred uterus" are being drafted under the auspices of the National College of obstetrics and gynecology (CNGOF) well highlighting the health problem public this represents. During 2011, 15% of the 2,700 patients who have recently given birth to the north of Marseille Hospital were carriers of a scarred uterus (internal data).The objective of the obstetrician is to ensure the welfare mother and fetus at the end of pregnancy and childbirth. To do this, the realization of a work being cesarean allows in some cases to reduce neonatal morbidity related to workflow especially in case of abnormal fetal pericardial pace that suggest fetal hypoxia. However, a significant number of caesarean section is performed by the side of caution during the second part of the work to a suspicion of non-engagement of the fetal presentation. These caesareans are indicated, rightly, before a clinical doubt about the height of the engagement of the fetal presentation in order to avoid making a difficult instrumental delivery, potentially harmful to the mother (perineal tear 3rd and 4th degree) and fetus (head injury, intracranial hemorrhage, cephalohematoma). A prospective study published in the Lancet estimated 37% error percentage attributable to the clinical examination in case of doubt on the commitment of presenatation fœtale. The CNGOF held through PRC publication what to do in case of obstetric clinical doubt about the commitment of the fetal presentation and "not recommended" no show against an instrumental extraction in this situation (RPC 2008).

Ultrasound has revolutionized pregnancy monitoring. Its routine use has in other prenatal diagnosis of fetal pathologies, it is the other reference screening tool of the most common obstetric pathology, preterm labor. Its use became widespread in the delivery room, the presence of an ultrasound machine is recommended by the decrees of perinatal care in maternity hospitals performing more than 1,500 deliveries per year. It is natural for conducting ultrasound during labor has emerged, first to help identify the variety of the presentation of the fetal head and then more recently in aid to instrumental delivery. Several studies have shown that ultrasound had a sensitivity of commitment over 90% for predicting the success of instrumental extraction and a vaginal delivery.

To our knowledge, to date, there is no study that investigated the benefit of ultrasound commitment to reduce the rate of cesarean section during labor. To answer this question, we want to show that making a commitment in case of diagnostic ultrasound of doubt about the level of engagement of the fetal head (4% of births) reduces by 30% the rate of caesarean section fully dilated.

Inclusion Criteria:

• Singleton pregnancy normal evolution> 37 weeks gestation
• Patient in labor with ruptured membranes, cephalic presentation, full dilatation since 2H, with doubts on clinical examination on the level of engagement of the fetal head in the maternal pelvis (0, +1, +2)

Exclusion Criteria:

• Abnormal fetal heart rate or suspected fetal acidosis on a scale pH

• No maternal indication for vaginal delivery or instrumental delivery

  • History of perineal tearing the 4th degree
  • Crohn's disease with involvement of the anal sphincter

• No fetal indication for instrumental delivery (suspected fetal thrombocytopenia)

• Other than fetal cephalic presentations