[1] Brown Univ, Sch Publ Hlth, Ctr Evidence Synth Hlth, Dept Epidemiol, Providence, RI USA
[2] Yale Sch Med, Dept Internal Med, New Haven, CT USA
[3] Univ Michigan, Med Sch, Dept Obstet & Gynecol, Ann Arbor, MI USA
[4] Peking Univ, Sch Publ Hlth, Dept Social Med & Hlth Educ, Beijing, Peoples R China
[5] Brown Univ, Sch Publ Hlth, Ctr Evidence Synth & Hlth, Providence, RI 02912 USA