 Normal full-term infants aged 0-28 days, from singlet pregnancy, born by vaginal delivery or by caesarian section, with Apgar score 7 in the 1st and 5th minute, not requiring resuscitation during delivery, and with a normal intrauterine growth, i.e. between 11th and 89th percentile AGA- appropriate for gestational age. The mothers medical history should be free of any chronic diseases and allergies, while the gestation history should be free of any complications and of any pharmaceutical treatment administration prior to delivery. 