1. Epidemiology Branch, Division of Intramural Population Health ResearchEunice Kennedy Shriver National Institute of Child Health and Human Development Bethesda Maryland USA
2. Program in Reproductive and Adult EndocrinologyEunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health Bethesda Maryland USA
3. Department of Obstetrics and GynecologyHoward University Hospital Washington DC USA
4. Department of Obstetrics and GynecologyUniversity of Utah Health Sciences Center Salt Lake City Utah USA
5. Department of StatisticsUniversity of Haifa Haifa Israel