The effects of cigarette smoking on circulating maternal leukocytes during pregnancy.

During pregnancy, cigarette smoke exposure, a common environmental insult, is damaging to both mother and fetus and is associated with pregnancy loss. The mechanism underlying the pathophysiology of injury is not understood. We hypothesized that smoking during pregnancy interferes with the normal physiological adaptation of the maternal immune system. We used flow cytometry to measure changes in the distribution of subsets of circulating leukocytes and adhesion molecule expression in a prospective cohort of 198 women who had 325 blood samples obtained throughout pregnancy. Smoking status was assessed by plasma cotinine concentration. Smoking increased the frequency of CD3(+) lymphocytes and decreased CD56(+) cells at 14-20 weeks gestation. Smoking also decreased the expression of CD54 on monocytes and CD62L on granulocytes throughout pregnancy. Our data demonstrate that smoking affects several immune parameters, especially early in pregnancy. These perturbations may play a role in pregnancy loss in women who smoke.