1. Division of General Internal Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
2. Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania.
3. Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania.
4. University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
5. Department of Biomedical Informatics, University of Pittsburgh, Pittsburgh, Pennsylvania.
6. Motherisk Laboratory, Hospital for Sick Children, Toronto, Ontario, Canada.