[1] Shahid Beheshti Univ Med Sci, Res Inst Childrens Hlth, Neonatal Hlth Res Ctr, Tehran, Iran
[2] Shahid Beheshti Univ Med Sci, Mahdieh Matern Hosp, Dept Neonatol, Tehran, Iran
[3] Univ Tehran Med Sci, Students Sci Res Ctr SSRC, Tehran, Iran
[4] Shahid Beheshti Univ Med Sci, Sch Publ Hlth & Safety, Dept Epidemiol, Tehran, Iran