[1] Univ Groningen, Univ Med Ctr Groningen, Beatrix Childrens Hosp, Div Neonatol,Dept Pediat, NL-9713 GZ Groningen, Netherlands
[2] Univ Groningen, Univ Med Ctr Groningen, Dept Epidemiol, NL-9713 GZ Groningen, Netherlands
[3] Univ Groningen, Univ Med Ctr Groningen, Dept Lab Med, NL-9713 GZ Groningen, Netherlands
[4] Univ Groningen, Univ Med Ctr Groningen, Beatrix Childrens Hosp, Div Endocrinol,Dept Pediat, NL-9713 GZ Groningen, Netherlands