1. Department of Obstetrics and Gynecology, University of Illinois at Chicago, Chicago, IL, USA;
2. Department of Obstetrics and Gynecology, Albert Einstein Medical Center, Philadelphia, PA, USA;
3. Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA;
4. Department of Obstetrics and Gynecology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, USA;
5. Division of Biostatistics, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, USA;
6. Department of Obstetrics and Gynecology, Geisinger Medical Center, Danville, PA, USA