1. Department of Obstetrics and Gynecology, University of Tennessee Health Science Center, Memphis, TN, USA;
2. Department of Obstetrics and Gynecology, University of South Florida, Tampa, FL, USA;
3. Department of Obstetric and Gynecology, University of North Dakota, Bismarck, ND, USA;
4. Department of Obstetrics and Gynecology, University of Louisville, Louisville, KY, USA;
5. Department of Biostatistics, Robert Stempel College of Public Health and Social Work, Florida International University, Miami, FL, USA;
6. Department of Pediatrics, University of Tennessee Health Science Center, Neonatology Division, Memphis, TN, USA