6-mercaptopurine (6-MP) has proven efficacy in the treatment of inflammatory bowel disease (IBD).
The teratogenicity of 6-MP has been demonstrated in animal studies at very high doses, however, human data suggest that 6-MP at maintenance doses is safe.
In this study, researchers from New York, USA, assessed the outcome of 72 pregnancies in patients with IBD. Patients had been previously treated with 6-MP at 3 different doses (50, 75, and 100 mg per day), for a median of 18 months. The research team also followed-up their children.
The team compared the outcome of pregnancies and development of offspring in 2 groups of patients. They assessed those patients with IBD who conceived 6 months to 22 years after stopping 6-MP (group 1) and patients with IBD who never received 6-MP prior to conception (group 2).
The researchers evaluated all pregnancies in terms of outcome. Outcomes included live full-term birth, premature delivery, stillbirth, spontaneous abortion, ectopic pregnancy, and therapeutic dilatation and curettage.
|Incidence of fetal loss:|
- 6-mercaptopurine = 29%
- control = 14%
|Journal of Clinical Gastroenterology|
The team also obtained data, regarding birth weight, congenital anomalies, and development, on all children.
Group 1 included 72 pregnancies carried by 29 women. The researchers found that in this group there were 51 live births (4 premature), 16 spontaneous abortions, 1 stillbirth, 2 therapeutic abortions due to abnormal amniocentesis, and 2 ectopic pregnancies.
The total incidence of fetal loss was 29%.
However, in group 2, 75 women had 140 pregnancies resulting in 120 live births (8 premature), 18 spontaneous abortions, and 2 stillbirths.
The team found that there were no cases of ectopic pregnancies or abnormal amniocentesis in group 2.
The total incidence of fetal loss was 14%.
They also found no increase in the incidence of developmental defects where mothers had been treated with 6-MP prior to pregnancy.
Dr Jusuf Zlatanic’s team concluded, “The incidence of fetal loss is higher in women with inflammatory bowel disease who had been previously treated with 6-MP compared with those who had not”.
“Whether this was related to the older age at conception in 6-MP group, longer duration of disease, initially more severe disease, or use of 6-MP we cannot tell.”