Department of Development and Regeneration (B.V.C.), KU Leuven, Herestraat 49 box 805, Leuven 3000, Belgium; Queen Charlotte's and Chelsea Hospital (T.B.), Imperial College, London, UK; Department of Obstetrics and Gynecology (W.F., D.T.), University Hospitals Leuven, Leuven, Belgium; Department of Clinical Sciences Malmö (L.V.), Lund University, Lund, Sweden.