title: Authors' reply.
authors: Department of Paediatrics, The Medical University of Warsaw, Poland.
authors: Marek
authors: M
authors: Ruszczyński
authors: Department of Paediatrics, The Medical University of Warsaw, Poland.
authors: Magdalena
authors: M
authors: Urbańska
authors: Department of Paediatrics, The Medical University of Warsaw, Poland.
authors: Hania
authors: H
authors: Szajewska