Smoking during pregnancy--hematological observations in the newborn.

Hematological values were measured in 28 newborn infants of mothers smoking 10-20 cigarettes daily during pregnancy, and in 25 infants of non-smokers. Higher hematocrit levels were found on the 1st day of life in infants of smoking mothers (60.8 +/- 5.0%, mean +/- S.D.) compared to controls (57.5 +/- 4.8%) (p less than 0.05). The hematocrit levels correlated positively with the maternal smoking level (r = 0.318, p less than 0.05) and the maternal serum thiocyanate concentrations at delivery (r = 0.389, p less than 0.01). Cord serum values for erythropoietin, serum-iron, transferrin and ferritin showed no statistically significant difference between the two groups. A significant inverse correlation was found between the hematocrit value on the 1st day of life and the cord serum ferritin concentration (r = -0.495, p less than 0.005). The present results suggest that maternal smoking stimulates fetal erythropoiesis, probably through a hypoxic effect on the fetus, dose related to the maternal smoking level. Increased erythropoiesis may cause increased iron incorporation into erythrocytes at expense of iron storage in the bone marrow and reticuloendothelial system.