[1] Univ Calif Berkeley, Sch Publ Hlth, Berkeley, CA 94720 USA
[2] Univ Milan, Sch Med, Hosp Desio, Dept Clin Pathol, I-20033 Desio, Italy
[3] Univ Calif Davis, Div Occupat Environm Med & Epidemiol, Davis, CA 95616 USA
[4] Univ Milan, Sch Med, Dept Obstet & Gynecol, I-20122 Milan, Italy
[5] Ctr Dis Control & Prevent, Natl Ctr Environm Hlth, Div Environm Hlth Lab Sci, Atlanta, GA 30333 USA