1. OBGYN, University of Cincinnati College of Medicine, Cincinnati, OH, USA;
2. Obstetrics and Gynaecology, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA;
3. Department of Mathematics, Columbia University, New York, NY, USA;
4. OBGYN, University of Texas Health Science Center at Houston, Houston, TX, USA;
5. University of Texas Health Science Center at Houston, Houston, TX, USA;
6. Department of Obstetrics, Gynaecology and Reproductive Sciences, Lyndon B. Johnson General Hospital, Houston, TX, USA;
7. Department of Obstetrics, Gynaecology & Reproductive Sciences, University of Texas Health Science Center, Houston, TX, USA;
8. Obstetrics and Gynaecology, University of Texas Health Science Center, Houston, TX, USA