Over the last few decades, the number of pregnant women under immunosuppressive (IS) therapy following transplantation or autoimmune diseases has increased. At first, IS drugs, including prednisone, azathioprine, and cyclosporine A were used, but now new molecules such as tacrolimus and mycophenolate mofetil have appeared. These IS drugs cross the placental barrier and enter into the fetal circulation, which poses a risk for fetal development. Experimental data have shown that IS drugs often have deleterious effects on fetuses, while human data have reported an increased rate of abortion, prematurity, intrauterine growth retardation (IUGR), and low birth weight, without significant increases in malformation rates. However, only limited information is available about the newly used molecules. Although fetal and neonatal data are reassuring, long-term effects of IS drugs on fertility, immune response and renal function, as well as the consequences of prematurity and IUGR, should be monitored.

ABSTRACT. Cyclosporin A (CsA) is an immunosuppressive agent used to prevent graft rejection and to treat autoimmune disorders. Successful pregnancies can be achieved among CsA-treated women, although it is known that CsA is nephrotoxic and crosses the human placenta. The aim of this study was to evaluate the harmlessness of CsA toward the embryonic kidney. Twenty-one pregnant rabbits were divided into four groups. Groups of six and four female animals were subjected to daily injections of 10 mg/kg per d CsA (administered subcutaneously) for 5 d, from day 14 to day 18 of gestation or from day 20 to day 24 of gestation, respectively. In the third group, five female animals received the CsA diluent (Cremophor) from day 14 to day 18 of gestation. The fourth group consisted of six untreated female animals. Pregnancy outcomes among CsA-treated does demonstrated a reduced number of living pups, which were also growth-retarded, with exposure to CsA from day 20 to day 24 of gestation. However, pups exposed to CsA from day 14 to day 18 of gestation exhibited normal fetal growth, and blood concentrations of CsA matched human data. Examinations of kidneys at birth demonstrated vacuolation of proximal and collecting tubules and ureteric bud ends. Increased glomerular volumes and decreased nephron densities suggested nephron mass reduction, which was quantitatively evaluated in 1-mo-old animals. The nephron numbers were reduced by 25 and 33% in day 14 to 18 CsA-treated and day 20 to 24 CsA-treated animals, respectively, which displayed compensatory adaptation of the existing nephrons. However, foci of segmental glomerular sclerosis were already present, which would possibly jeopardize renal function later in life.