Problem : Pregnancy-associated immunologic alterations may improve the course of asthma. Severe maternal asthma with an exacerbation impairs fetal growth. ; Method of study : Lymphocyte activation was estimated by flow cytometry analysis of surface markers in non-pregnant healthy and mild or moderate persistent asthmatic women and healthy as well as mild or moderate persistent asthmatic, third trimester pregnant women. ; Results : Compared with non-pregnant healthy subjects (n = 12) activated pools within CD4 and CD8 T cells were larger and the number of NK T cells were increased both in non-pregnant asthmatic (n = 12) and in healthy pregnant (n = 13) subjects (all p