Pregnancy outcome after paternal exposure to azathioprine/6-mercaptopurine.

There are only few studies with conflicting results on pregnancy outcome after paternal exposure to azathioprine or 6-mercaptopurine. In our study, pregnancy outcome of 115 prospectively followed pregnancies after paternal exposure to azathioprine or 6-mercaptopurine is compared to a control group of 341 pregnancies. The rate of major malformations was not increased (3.0% in exposed versus 2.2% in the control group). There was no specific pattern of birth defects and no indication for chromosomal aberrations in the exposed group. We observed a higher rate of elective terminations of pregnancy in the exposed group and a non-significant increase of spontaneous abortions (cumulative incidence 19% versus 13%, respectively). Further prospective studies are required to address the question of a possibly increased risk for spontaneous abortion.