1. Division of Maternal Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas
2. Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, Texas
3. Children's Memorial Hermann Hospital, The Women's Center, Labor and Delivery, Houston, Texas