[1] Univ N Carolina, Dept Epidemiol, Chapel Hill, NC USA
[2] Massachusetts Gen Hosp, Dept Obstet & Gynecol, Boston, MA USA
[3] Univ N Carolina, Lineberger Comprehens Canc Ctr, Chapel Hill, NC USA
[4] Kaiser Permanente Southern Calif, Pasadena, CA USA
[5] Kaiser Permanente Northern Calif, Oakland, CA USA
[6] Univ N Carolina, Dept Obstet & Gynecol, Chapel Hill, NC USA
[7] Univ N Carolina, Gillings Sch Global Publ Hlth, Dept Epidemiol, 135 Dauer Dr, Chapel Hill, NC 27599 USA