[1] Univ MN, Sch Publ Hlth, Div Epidemiol & Community Hlth, Minneapolis, MN USA
[2] Univ Minnesota, Sch Med, Dept Pediat, Div Neonatol, Minneapolis, MN USA
[3] Univ Minnesota, Clinicial & Translat Sci Inst, Minneapolis, MN USA
[4] Univ Minnesota, Sch Med, Dept Pediat Neonatol, Div Neonatol, Acad Off Bldg,2450 Riverside Ave S, Minneapolis, MN 55454 USA