F Envain1, C Garabedian2. 1. CHU Lille, Department of Obstetrics, F-59000 Lille, France. Electronic address: francois.envain.pro@gmail.com. 2. Univ. Lille, CHU Lille, ULR 2694 - METRICS, F-59000 Lille, France; CHU Lille, Department of Obstetrics, F-59000 Lille, France.