1. Reproductive Epidemiology Section, Environmental Health Investigations Branch, California Department of Health Services, Oakland, CA, USA,
2. Reproductive Epidemiology Section, Environmental Health Investigations Branch, California Department of Health Services, Oakland, CA, and Kaiser Permanente Medical Care Group, Division of Research, Oakland, CA, USA,
3. Reproductive Epidemiology Section, Environmental Health Investigations Branch, California Department of Health Services, Oakland, CA, USA