1. Leiden University Medical Center; Gynaecology, Division of Reproductive Medicine and Dept. of Clinical Epidemiology; PO Box 9600 Albinusdreef 2 Leiden Netherlands NL 2300 RC
2. Leiden University Medical Center; Gynaecology, Division of Reproductive Medicine; Albinusdreef 2 Leiden Netherlands NL 2300 RC
3. Slotervaart hospital; Department of Obstetrics and Gynaecology; Unknown Louwesweg Netherlands 1066
4. Leiden university Medical Center; Pediatrics and Clinical Epidemology; P.O. Box 9600 Leiden Netherlands 2300 RC
5. FHI; Behavioral and Biomedical Research; PO Box 13950 Research Triangle Park North Carolina USA NC 27709