1. Department of Obstetrics and Gynecology, The Permanente Medical Group, Oakland, California
2. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, The Permanente Medical Group, Oakland, California
3. Division of Research, Kaiser Permanente Northern California, Oakland, and the Department of Health Systems Science, Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, California