Teratogenesis and immunosuppressive treatment.

Despite the potential risks to the mother and fetus caused by immunosuppressive drugs, uneventful pregnancies are now frequent among transplant recipients. Although there is no apparent increase in the type or incidence of malformations in the newborns or evidence of graft dysfunction, pregnancy-related complications, including premature termination and low birth weight, may be more frequent. To prevent graft rejection due to the increased immunologic reactivity of the transplant recipient during pregnancy, it is reasonable to wait 2 years after transplantation before conception, to have stable graft function and to be on low drug doses for maintenance immunosuppression. Among the immunosuppressive agents, corticosteroids may induce a number of treatment-related complications, including diabetes and osteoporosis; however, the incidence of fetal malformations during corticosteroid treatment is about 3.5%, a value close to that of the general population. Among immunosuppressive antibodies, no evidence of developmental toxicity has been demonstrated with basiliximab. On the contrary, some concerns have been raised about azathioprine, since its use has been associated with fetal abnormalities in animals; however, clinical data so far have indicated only a small teratogenic risk. Therefore, immunosuppressive therapy with selected drugs and antibodies does not apparently increase the risk of birth defects and may be continued in pregnancy. Finally, although breast-feeding is not recommended, because of drug transfer into maternal milk, the available clinical data do not support this limitation because of the low amount of drug absorbed by the infant and the absence of clinical toxicity in published case reports.