[1] Institute of Paediatrics,
[2] Karol Marcinkowski University of Medical Sciences,undefined
[3] Szpitalna 27/33,undefined
[4] 60-572 Poznan,undefined
[5] Poland e-mail: jarwalk@sk5.usoms.poznan.pl Tel.: +48-61-8472685; Fax: +48-61-8483362,undefined