Exposure to Mycophenolate and Fatherhood.

Background: Mycophenolic acid (MPA) is the active immunosuppressive substance in both mycophenolate mofetil and mycophenolate sodium, and it is widely used after organ transplantation. In women, taking MPA is teratogenic and may also influence spermatogenesis. There is a lack of knowledge regarding outcome of pregnancies fathered by men exposed to MPA.

Methods: We compared outcomes in pregnancies fathered by renal transplant men per whether they had been exposed to MPA or not at time of conception. A nationwide population-based retrospective cohort study was performed. Data from the Norwegian Renal Registry with all renal transplanted men alive between January 1, 1995 and December 31, 2015 were included, and relevant outcome data were extracted from the Medical Birth Registry of Norway.

Results: During the given time, 230 immunosuppressed renal transplanted men fathered 350 children (155 on MPA/195 not on MPA). There were no significant increased risks of malformation (3.9% vs. 2.6%, P = 0.49) in MPA exposed versus unexposed cohorts of children. The average dose (±SD) of mycophenolate was 1.42 ± 0.3 g/day and the individual median MPA trough concentration in the time period of anticipated conception and pregnancy was 2.8 ± 1.6 mg/L. Birth weight was similar in exposed and unexposed cohorts of children; 3381 ± 681 g vs. 3429 ± 714 g (P = 0.53).

Conclusions: Paternal exposure to MPA did not increase the risk of adverse birth outcomes in children fathered by male kidney transplanted patients. These results are reassuring and support the continuation of paternal MPA treatment before, during, and after conception.