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.