One of the most important immunological modifications during pregnancy is the Th1/Th2 shift, due to the progressive increase of progesterone and estrogens during pregnancy, which reach their peak-level in the third trimester of gestation. At high levels, estrogens seem mainly to suppress Th1 cytokines and stimulate Th2-mediated immunological responses as well as antibody production. For this reason Th1-mediated diseases, like rheumatoid arthritis (RA), tend to improve and Th2-mediated disease, like systemic lupus erythematosus (SLE), tend to worsen during pregnancy. SLE is the autoimmune rheumatic disease in which pregnancy most frequently occurs because it predominantly affects young females in their childbearing age. Other autoimmune rheumatic diseases, including RA, are less frequently observed during pregnancy due to their low female-to-male ratio and peak onset after the age of 40. This review is focused on the disease course, gestational outcome and management of patients with SLE and RA during pregnancy.