(1) Unremarkable medical history (no perinatal antibiotics, no underlying disease, not hospitalized longer than the mother), (2) Good appearance, (3) No focal physical signs of infection, (4) CRP level < 1 mg/dl, (5) WBC 5000-15000 counts/mm3 and band/neutrophil ratio (I/T) <0.2, (6) A normal urine analysis.