1 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University, New York, NY, USA.
2 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Texas Medical Branch at Galveston, Galveston, TX, USA.
3 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, McGovern Medical School-University of Texas at Houston, Houston, TX, USA.