The purpose of this study is to evaluate if regulator T cells (Treg) and Th17 level modifications in maternal blood and placenta could be correlated to a chorioamnionitis, in women hospitalized for PPROM.

Acute chorioamnionitis is the principal antecedent of premature birth and an important contributor to specific neonatal and other complications that may extend throughout subsequent life. The PPROM is a high risk condition for developing chorioamnionitis. Available biological markers have a low prognostic value. Indeed, currently the diagnosis of intra-uterine infection relies only on placental cultures and anatomo-pathological exam after the delivery.

Moreover, pregnancy is an immunologic particular condition. Indeed an immune tolerance is required with respect to the fetus and is mediated by Treg lymphocytes, which suppressed Th17 activity.

Recent studies have shown among women with frequent miscarriages, a balance between Treg and Th17, with a decrease in Treg number and an increase in Th17 number in decidua and blood.

In case of infection, the immune pro-inflammatory response (Th17) is restored in peripheric tissues and in blood in order to limit the extention of intra-uterine infection. This restoration of this pro-inflammatory response could be due to a modification of Treg number ou tolerogenic activity.

In this context, our hypothesis is that chorioamnionitis will lead to a decrease of treg proportion and an increase of Th17 proportion in lymphocyte populations of maternal blood and placenta, with a back to values near than which is observed in beginning of pregnancy or in no pregnant women.

Inclusion Criteria:

• Informed consent signed
• Patient affiliated with a social security scheme
• term pregnancy betwwen 24 and 34 weeks
• PPROM diagnosis
• singleton pregnancy

Exclusion Criteria:

• delivery occured in 1 hour after admission
• hemorragic praevia placenta or retro-placental hematoma
• confirmed autoimmune or inflammatory disease
• confirmed infectious disease by VIH, VHC, and VHB