[1] Univ Alabama Birmingham, Dept Pediat, Birmingham, AL 35249 USA
[2] Res Triangle Inst, Res Triangle Pk, NC 27709 USA
[3] Case Western Reserve Univ, Dept Pediat, Cleveland, OH 44106 USA
[4] Emory Univ, Dept Pediat, Atlanta, GA 30322 USA
[5] Yale Univ, Dept Pediat, New Haven, CT USA
[6] NICHHD, Neonatal Res Network, Bethesda, MD 20892 USA