In physiological conditions, newborns have low white blood cells, but usually not less than 12,000/μL, while in pathological conditions, such as drugs, infections, blood diseases, etc. can cause abnormally low white blood cells. 1. Medications: Consumption or misuse of certain medications such as propylthiouracil, a drug used to treat hyperthyroidism, can cause serious side effects such as granulocyte deficiency. 2. Viruses or bacteria: such as colds, tuberculosis, etc. cause bone marrow suppression in newborns, producing fewer white blood cells, which can also lead to low white blood cells in newborns. 3. Blood diseases: such as congenital granulocyte deficiency, leukemia, etc., inhibit bone marrow hematopoiesis, which can lead to low white blood cells. If you find that your newborn has low white blood cells, you should seek professional medical advice and receive regular treatment.