[1] NU Hosp Grp, Dept Pediat, Uddevalla, Sweden
[2] Univ Gothenburg, Sahlgrenska Acad, Inst Clin Sci, Dept Pediat, Gothenburg, Sweden
[3] Karolinska Univ Hosp, Dept Pediat Surg, Stockholm, Sweden
[4] Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden