Immunosuppressive drugs given during pregnancy to mothers suffering from a systemic autoimmune disease (AID) can cross the placenta, thus being potentially able to affect the offspring immune system. Aim of our study was to evaluate the in vivo immune function of a series of these newborns. Twenty-two babies born from mothers suffering from autoimmune diseases (AID) who had been taking immunosuppressive drugs during pregnancy were evaluated for their response to vaccination with C. Tetani toxoid. Six babies born from mothers receiving low-dose aspirin only were used as controls. The immune response to C. Tetani vaccination was evaluated with an ELISA to detect circulating antibodies. Five children out of 28 (17%) did not achieve a protective titer of anti C. Tetani toxoid IgG. No clear relationship was found between specific drug exposure and antibody response. Our findings suggest that maternal immunosuppressive treatment given for a systemic AID can affect the response to an active immunization, without specificities for drug types used.