1. Department of Obstetrics and Gynecology, The Ohio State University College of Medicine, Columbus, OH, USA;
2. George Washington University Biostatistics Center, Washington, DC, USA;
3. University of Utah Health Sciences Center, Salt Lake City, UT, USA;
4. Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX, USA;
5. Department of Obstetrics and Gynecology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA;
6. Department of Obstetrics and Gynecology, Columbia University, New York, NY, USA;
7. Department of Obstetrics and Gynecology, Brown University, Providence, RI, USA;
8. Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, AL, USA;
9. Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, NC, USA;
10. Department of Obstetrics and Gynecology, Case Western Reserve University-MetroHealth Medical Center, Cleveland, OH, USA;
11. University of Texas Medical Branch, Galveston, TX, USA;
12. Department of Obstetrics and Gynecology, Northwestern University, Chicago, IL, USA;
13. University of Texas Health Science Center at Houston-Children’s Memorial Hermann Hospital, Houston, TX, USA;
14. Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC, USA;