1. Department of Pediatric Research, New York State Institute for Basic Research in Mental Retardation, Staten Island 10314
2. Department of Pediatric Research, New York State Institute for Basic Research in Mental Retardation, and Department of Pediatrics, Mt. Sinai Hospital School of Medicine, New York 10029
3. I and II Clinic of Obstetrics and Gynaecology, Helsinki University Central Hospital, Helsinki 29, Finland