The practice of ultrasounds increases in delivery rooms every year. Indeed, this method can help to visualize elements that may not be observable after clinical examination. Moreover, it is known that a fetal head engagement can lead to an instrumental extraction and in case of error, which happens in some cases, fetal and maternal risks are possible.

These elements led to the investigators' hypothesis which is that a trans-perineal ultrasonography may facilitate the evaluation of a clinical fetal head engagement in case of doubt.

It's a monocentric, transversal, clinical trial regarding women giving birth at the GHICL's hospital Saint Vincent de Paul.

Clinical examinations will be done by the midwives following the indications given on the clinical form. A trans-perineal echography will then be done by technical operators following the ultrasonography form.

These examinations will only last a few minutes, no further tests will be done afterwards.

Inclusion Criteria:

• Patients of 18 years old or older
• Primiparous
• Complete dilation of the cervix
• Gestational age of 37 weeks or more according to the date of amenorrhea - - Rupture of membranes
• Fetus in cephalic presentation
• Patient who has signed a consent form

Exclusion Criteria

• Patient for whom the fetus has died in uteri
• Patient who's coming for an abortion
• Fetus in breech or transverse presentation
• Gemellary pregnancy for which the fetus present a severe cardiac anomaly
• Patient under trusteeship or guardianship

Patients included are women about to give birth, they undergo a clinical examination done by midwives. Followed by a trans-perineal ultrasonography examination done by a technical operator in order to measure the perineal-cephalic distance.

These examination are done the day of enrollment, they last for a few minutes and no further tests will be done afterwards.