作者单位:Univ N Carolina, Dept Family Med, Chapel Hill, NC USA[1]Univ N Carolina, North Carolina Translat & Clin Sci Inst, Chapel Hill, NC USA[2]Univ N Carolina, Dept Epidemiol, Gillings Sch Global Publ Hlth, Chapel Hill, NC USA[3]Univ N Carolina, Dept Obstet & Gynecol, Chapel Hill, NC 27599 USA[4]