Hematologic, Immunologic, and Neoplastic Disorders Practice Test

Right after birth, the newborn’s white blood cell count is elevated as part of normal adaptation to life outside the womb. This physiologic leukocytosis peaks at birth and then rapidly normalizes as the immune system adjusts. By about one week, the WBC count has typically stabilized toward the normal pediatric/adult range. Longer timeframes like two weeks, a month, or six months would not reflect this rapid postnatal adjustment, which is why about one week is the best answer.