The effect of smoking during pregnancy on cord blood and maternal serum immunoglobulin levels.

The effect of smoking on the fetal and maternal humoral immune parameters was evaluated in cord and maternal blood, collected at delivery from 163 mothers who smoked and 130 mothers who did not smoke, and their offspring. There was no difference in time of gestation between the two groups, but the mean birth weight of the offspring of mothers who smoked was decreased, as previously observed. There were higher levels of IgA (p less than 0.01), IgM (p less than 0.001), and IgG (p less than 0.001) in cord sera of children of mothers who smoked than in the offspring of mothers who did not smoke. Mothers themselves who smoked had higher levels of IgM (p less than 0.001) and IgG (p less than 0.001), but not IgA, as compared to control mothers who did not smoke. Since cord IgA and IgM are produced by the fetus, these results could be interpreted as being due to either a higher incidence of infection in utero or metabolic differences in the children of mothers who smoke. Either of these possibilities may explain the increased frequency of postpartum endometritis, increased incidence of fetal distress, and the characteristic of meconium-stained amniotic fluid in mothers who smoke.