OBJECTIVE To evaluate whether the absolute nucleated red blood cell (RBC) count is elevated in term, appropriate for gestational age (AGA) infants born to smoking women. METHODS We compared absolute nucleated RBC counts taken during the first 12 hours of life in two groups of term, vaginally delivered, AGA infants, one group born to mothers who smoked during pregnancy (n = 30) and the other born to mothers who did not smoke (n = 30). We excluded infants of women with diabetes, hypertension, or alcohol or drug abuse, and infants with heart rate abnormalities, hemolysis, blood loss, or chromosomal anomalies. RESULTS There were no differences between the groups in birth weight, gestational age, maternal age, gravidity, parity, maternal analgesia during labor, 1- and 5-minute Apgar scores, corrected white blood cell counts, lymphocyte counts, or hematocrits. The median absolute nucleated RBC count in infants of smoking mothers was 0.5 x 10(9)/L (range 0 to 5.0) versus 0.0005 x 10(9)/L (range 0 to 0.6) in nonsmoking controls (P < .002). Regression analysis that included Apgar scores, gestational age, and number of cigarettes smoked per day showed a significant correlation of absolute nucleated RBC count only with the number of cigarettes smoked per day (P < .001). CONCLUSIONS At birth, term AGA infants born to smoking mothers have increased circulating absolute nucleated RBC counts compared with controls. The absolute nucleated RBC count in newborns correlates with the number of cigarettes smoked during pregnancy.