[1] Univ Calif Los Angeles, David Geffen Sch Med, Div Digest Dis, Los Angeles, CA 90095 USA
[2] Beth Israel Deaconess Med Ctr, Ctr Inflammatory Bowel Dis, Boston, MA 02215 USA
[3] Harvard Univ, Sch Med, Boston, MA USA
[4] Beth Israel Deaconess Med Ctr, Dept Obstet & Gynecol, Boston, MA 02215 USA
[5] Brigham & Womens Hosp, Dept Obstet Gynecol & Reprod Biol, Boston, MA 02115 USA
[6] Harvard Univ, Sch Publ Hlth, Dept Epidemiol, Boston, MA 02115 USA
[7] Brigham & Womens Hosp, Dept Med, Channing Div Network Med, Boston, MA 02115 USA
[8] Brigham & Womens Hosp, Ctr Crohns & Colitis, Boston, MA 02115 USA