1 Maccabi Health Services, Tel Aviv, Israel. Electronic address: zgrosman@netvision.net.il.
2 Department of Paediatrics, Schnaeider Children's Medical Center, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
3 Department of Maternal and Child Health, Public Health Service, Ministry of Health, Jerusalem, Israel; School of Public Health, University of Haifa, Haifa, Israel.