1 Merck KGaA, Frankfurter Str. 250, Post Code: F135/002, 64293, Darmstadt, Germany; Department of Development and Regeneration, Biomedical Sciences, University of Leuven (KU Leuven), p/a University Hospital Gasthuisberg, Department of Obstetrics and Gynecology, Herestraat 49, 3000 Leuven, Belgium. Electronic address: thomas.dhooghe@merckgroup.com.