[1] Univ N Carolina, Dept Dent Ecol Dent Res, Chapel Hill, NC USA
[2] Univ N Carolina, Dept Periodontol, Chapel Hill, NC USA
[3] Univ N Carolina, Data & Stat Coordinating Ctr, Chapel Hill, NC USA
[4] Duke Univ, Dept Maternal Fetal Med, Durham, NC USA
[5] Univ Texas Hlth Sci Ctr San Antonio, Dept Periodont, San Antonio, TX 78229 USA
[6] Univ Texas Hlth Sci Ctr San Antonio, Dept Obstet & Gynecol, San Antonio, TX 78229 USA
[7] Univ Alabama Birmingham, Dept Periodontol, Birmingham, AL USA
[8] Univ Alabama Birmingham, Dept Obstet & Gynecol, Birmingham, AL 35294 USA
[9] Univ N Carolina, Dept Biostat, Chapel Hill, NC USA