Outcome of pregnancies when fathers are treated with 6-mercaptopurine for inflammatory bowel disease

The outcomes of pregnancies after maternal use of 6-mercaptopurine (6-MP) for inflammatory bowel disease (IBD) during pregnancy have been reported, but data are lacking for outcomes when the fathers use this drug.

Subjects were male patients with IBD seen at one center between 1970 and 1997. Patients and their wives were interviewed. Group 1 comprised pregnancies fathered by men who were taking 6-MP. This group was further subdivided into those conceived within 3 months of 6-MP use and those conceived at least 3 months after 6-MP was stopped. Group 2 comprised pregnancies fathered by men with IBD, similar in characteristics to group 1, who had not taken 6-MP before fertilization. Information was collected regarding the fathers, the mothers, and the pregnancies, as well as the health of the children, in a historical cohort study.

There were 50 pregnancies in group 1 (13 in 1A and 37 in 1B) and 90 pregnancies in group 2. Four of the 13 pregnancies in group 1A were associated with complications. There were two spontaneous abortions, and two congenital anomalies including a missing thumb in one and acrania with multiple digital and limb abnormalities in the other. Risk of complications was significantly increased when compared with group 1B (p < 0.013) and group 2 (p < 0.002).

The incidence of pregnancy-related complications was significantly increased when the fathers used 6-MP within 3 months of conception.