[1] Univ North Carolina Chapel Hill, Gillings Sch Global Publ Hlth, Dept Epidemiol, Chapel Hill, NC USA
[2] Univ North Carolina Chapel Hill, Carolina Populat Ctr, Chapel Hill, NC USA
[3] Univ North Carolina Chapel Hill, Sch Med, Chapel Hill, NC USA
[4] Northwestern Univ, Feinberg Sch Med, Dept Med Social Sci, Chicago, IL USA
[5] Metrohlth Med Syst, Populat Hlth Equ Res Inst, Ctr Hlth Care Res & Policy, Cleveland, OH USA
[6] Case Western Reserve Univ, Sch Med, Cleveland, OH USA
[7] Univ Texas Austin, Steve Hicks Sch Social Work, Dept Sociol, Austin, TX USA
[8] Univ Alabama Birmingham, Dept Obstet & Gynecol, Birmingham, AL USA
[9] Univ Calif San Francisco, Dept Obstet & Gynecol, San Francisco, CA USA
[10] Brown Univ, Warren Alpert Med Sch, Dept Obstet & Gynecol, Div Maternal Fetal Med, Providence, RI USA
[11] Univ North Carolina Chapel Hill, Dept Obstet & Gynecol, Chapel Hill, NC USA
[12] Univ North Carolina Chapel Hill, Dept Epidemiol, Chapel Hill, NC 27599 USA