Treating inflammatory bowel disease during pregnancy: risks and safety of drug therapy.

The safety of drug therapy for inflammatory bowel disease during pregnancy is an important clinical concern. Current available information is largely derived from animal studies and clinical experience among patients with inflammatory bowel disease and autoimmune disorders and organ transplant recipients. However, these data are confounded by various factors including difficulty projecting the results of animal studies to humans, methodological deficiencies of some studies, insufficient experience with certain agents, difficulty distinguishing the fetal effects of underlying disease from drug therapy and a need to consider the impact of background rates of adverse fetal outcomes which apply to all pregnancies. In inflammatory bowel disease, the effects of active inflammation on the fetus are believed to be more harmful than those of drug treatment, and therapy is often justified to induce or maintain remission during pregnancy. The choice of appropriate treatment is determined by the severity of the disease and the potential for drug toxicity. No causal relationship has been established between exposure to sulfasalazine or other 5-aminosalicylic acid drugs and the development of congenital malformations. These drugs may be used with relative safety during pregnancy and lactation. Considerable experience with corticosteroids have shown them to pose very small risk to the developing fetus. Current evidence indicates that maternal use of azathioprine is not associated with an increased risk of congenital malformations, though impaired fetal immunity, growth retardation or prematurity is occasionally observed. Preliminary evidence derived from patients with inflammatory bowel disease show no significant fetal toxicity following first trimester exposure to mercaptopurine, though its elective use in pregnancy is controversial. Cyclosporin is not teratogenic, but may be associated with growth retardation and prematurity. Pregnancy should be avoided in women treated with methotrexate because of its known abortifacient effects and risk of causing typical malformations. Although treatment with metronidazole or ciprofloxacin for short durations appear to be devoid of adverse fetal reactions, the effect of prolonged exposure as required in Crohn's disease remains unknown.