[1] Univ Hawaii, Ctr Canc, Canc Epidemiol Program, Honolulu, HI 96822 USA
[2] Cincinnati Childrens Hosp Med Ctr, Div Biostat & Epidemiol, Cincinnati, OH 45229 USA
[3] Dalhousie Univ, Dept Obstet, Halifax, NS, Canada
[4] Dalhousie Univ, Dept Gynecol, Halifax, NS, Canada
[5] Dalhousie Univ, Dept Pediat, Halifax, NS, Canada
[6] Univ So Calif, Keck Sch Med, Dept Prevent Med, Los Angeles, CA 90033 USA