Prolongation of pregnancy at and beyond 41 completed weeks occurs in 16.8 % of pregnancies in France [1]. It is associated with a significant increase in perinatal morbidity (low umbilical artery pH, 5-min Apgar score < 7, admission to neonatal intensive care unit (NICU), and intrapartum asphyxia), and mortality [2].

The indicators used in most international clinical guidelines to identify a possible placental insufficiency and to consider labor induction are decreased fetal movements, FHR abnormalities, and oligohydramnios [[3], [4], [5], [6]]. However, these criteria occur very late, their sensitivity and specificity are very poor [4] and their use is not associated with any proven improvement in the neonatal status.

Other parameters could be used to assess a possible late placental insufficiency [7], including Doppler of the umbilical artery, fetal middle cerebral artery and cerebro-placental ratio (CPR).

The use of doppler has increased since 2012 [8], due to their apparent relation placental insufficiency.

However, publications about CPR in prolonged pregnancies are rare.

Moreover, a recent study suggested that lower CPR could be associated with operative delivery mainly at and beyond 40 weeks [9].

Our aim was to assess in a prospective and blinded manner, the association of umbilical artery resistance index (UA-RI), middle cerebral artery resistance index (MCA-RI) and CPR with the likelihood of medical interventions during labor and perinatal complications in pregnancies at/or beyond 41 weeks.