1. Department ofObstetrics and Gynecology; University of Cincinnati; Cincinnati OH USA
2. The George Washington University Biostatistics Center; Washington DC USA
3. Obstetrics, Gynecology and Reproductive Science; University of Pittsburgh; Pittsburgh PA USA
4. The Eunice Kennedy Shriver National Institute of Child Health and Human Development; Bethesda MD USA
5. Obstetrics and Gynecology; Columbia University; New York NY USA
6. Obstetrics and Gynecology; University of North Carolina at Chapel Hill; Chapel Hill NC USA
7. Maternal Fetal Medicine; Case Western Reserve University-MetroHealth Medical Center; Cleveland OH USA
8. Obstetrics and Gynecology; Northwestern University; Chicago IL USA
9. Obstetrics, Gynecology and Reproductive Science; University of Texas Health Science Center at Houston; Houston TX USA
10. Obstetrics and Gynecology; Brown University; Providence RI USA
11. Obstetrics and Gynecology; Christiana Care Health System; Newark DE USA
12. Obstetrics and Gynecology; Oregon Health & Science University; Portland OR USA
13. Obstetrics and Gynecology; University of Texas Medical Branch; Galveston TX USA
14. Obstetrics and Gynecology; Wayne State University; Detroit MI USA