1. Epidemiology Branch; Division of Intramural Population Health Research; Eunice Kennedy Shriver National Institute of Child Health and Human Development; Bethesda MD USA
2. Biostatistics Branch; Division of Cancer Epidemiology and Genetics; Medical Center Drive; National Cancer Institute; Rockville MD USA
3. Department of Obstetrics and Gynecology; Feinberg School of Medicine; Northwestern University; Chicago IL USA
4. Department of Obstetrics and Gynecology; Medical University of South Carolina; Charleston SC USA
5. Department of Ob/Gyn; The University of Alabama at Birmingham Center for Women's Reproductive Health; Birmingham AL USA
6. Division of Maternal-Fetal Medicine; Department of Obstetrics-Gynecology; School of Medicine; University of California, Irvine; Orange CA USA
7. Miller Children's Hospital/Long Beach Memorial Medical Center; Long Beach CA USA