1. Department of Obstetrics and Gynecology; Hospital of the University of Pennsylvania; Philadelphia PA USA
2. Department of Obstetrics and Gynecology, Center for Research on Reproduction and Women's Health; Hospital of the University of Pennsylvania; Philadelphia PA USA
3. Department of Obstetrics and Gynecology; Weill Cornell Medical College; New York NY USA
4. Department of Biostatistics, Epidemiology and Informatics; University of Pennsylvania Perelman School of Medicine; Philadelphia PA USA