1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
2. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, The Ohio State University, Columbus, Ohio, USA.
3. Department of Preventive Medicine, Biostatistics Collaboration Center, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
4. Division of General Internal Medicine, Department of Medicine and Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
5. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.