The safety of mesalamine in human pregnancy: A prospective controlled cohort study

Background & Aims: Mesalamine is a first-line drug in the treatment of inflammatory bowel disease. Information regarding human pregnancy experience with mesalamine has been scarce and uncontrolled despite its frequent use in women of childbearing age. The aim of this study was to examine the fetal safety of mesalamine. Methods: The Motherisk Program prospectively enrolled and followed up 165 women exposed to mesalamine during pregnancy, 146 of whom had first trimester exposure. Pregnancy outcome was compared with that of a matched control group, who were counseled for nonteratogenic exposure. Results: There was no increase in major malformations (1 of 127 [0.8%] for mesalamine vs. 5 of 131 [3.8%] for nonteratogenic controls; P = 0.23). There was an increase in the rate of preterm deliveries (13.0% for mesalamine vs. 4.7% for nonteratogenic controls; P = 0.02), a decrease in the mean maternal weight gain during pregnancy (13.1 +/- 6.3 kg for mesalamine vs. 15.6 +/- 6.0 kg for nonteratogenic controls; P = 0.0002), and a decrease in the mean birth weight (3253 +/- 546 g for mesalamine vs. 3461 +/- 542 g for nonteratogenic controls; P = 0.0005). There were no significant differences in the maternal obstetric history, rates of live births, miscarriages, pregnancy terminations, ectopic pregnancies, delivery method, or fetal distress between the groups. Conclusions: This study suggests that mesalamine does not represent a major teratogenic risk in humans when used in the recommended doses.