1. Department of Obstetrics and Gynecology, Kaiser Permanente San Francisco, San Francisco, CA, USA
2. Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, OR, USA
3. Department of Pediatrics, University of California, Davis, Davis, CA, USA
4. San Gabriel Valley Perinatal Medical Group, Division of Maternal Fetal Medicine, Pomona Valley Hospital Medical Center, Pomona, CA, USA