The purpose of this study is to determine whether, in a high risk population (placenta praevia and previous caesarean or prenatal suspicion of morbidly adherent placenta (MAP)), the concentration of cell-free fetal DNA circulating in the maternal plasma is significantly increased in the subgroup of morbidly adherent placenta (MAP) cases , in order to determine if the dosage of cell-free fetal DNA circulating in the maternal plasma may be a useful biological tool to detect MAP, alone or in addition to the imagery findings (ultrasonography and RMI).

Background: Morbidly adherent placenta (MAP) is a life-threatening condition characterized by placental villi being abnormally adherent to the myometrium. Prenatal identification of MAP is essential to anticipate the risk and plan optimal delivery conditions for these women while this is associated to a maternal outcome improvement. Prenatal identification based on Doppler ultrasound and/or MRI is associated with high rates of false-positive or false-negative findings responsible for adverse effects. Some cases reports have suggested that the concentration of cell-free fetal DNA circulating in the maternal plasma is significantly increased in a context of morbidly adherent placenta (MAP).

Objective: The primary objective is to determine whether the concentration of cell-free fetal DNA circulating in the maternal plasma is significantly increased in women with morbidly adherent placenta (MAP) compared to women with placenta praevia and previous caesarean. Secondary objectives are to determine whether cell-free fetal DNA circulating in the maternal plasma is a useful biological tool to detect MAP, alone or in addition to the imagery findings (ultrasonography and RMI), in a high risk population (placenta praevia and previous caesarean or only prenatal suspicion of MAP).

Design: Prospective observational study of pregnant women with placenta praevia and previous cesaeran or with prenatal suspicion of placenta accreta, conducted in 5 centers.

Methods: We expect to include 83 women at risk of MAP in two years, of whom approximately 17 (20%) will have a MAP.

Main outcome measures: The primary outcome measure is concentration of cell-free fetal DNA circulating in maternal plasma.

Conclusion: This study will be the first prospective study to include women at risk of placenta accreta and to investigate whether the concentration of cell-free fetal DNA circulating in maternal plasma is increased in MAP women and whether it is a useful biological marker to detect prenatally MAP in a high risk population.

Inclusion Criteria:

Every woman:

• delivering in one of the 5 maternity units that participate to a Population-based prospective observational study of pregnant women with a placenta praevia and previous cesarean or with prenatal suspicion of accreta (PACCRETA) .
• With a placenta praevia and at least one previous cesarean delivery or having a prenatal suspicion of placenta accreta
• aged 18 or more

Exclusion Criteria:

Every woman:

• not understanding French.
• refusing to participate in the study

Women delivering in 5 maternity units that participate in a Population-based prospective observational study of pregnant women with a placenta praevia and previous cesarean or with prenatal suspicion of accreta (PACCRETA)