Background: Crohn's disease (CD) is associated with increased risk of adverse birth outcomes. However, existing studies have not taken into account the impact of drug treatment. We examined the impact of drug treatment on birth outcomes--low birth weight (LBW), preterm birth, LBW at term, and congenital abnormalities (CAs)--among CD women.
Methods: A nationwide Danish cohort study of 900 children born to CD women between 1996 and 2004, based on the National Registry of Patients, the Birth Registry, and the nationwide prescription database. Pregnancies were classified according to receipt of prescriptions for CD medication: no drugs (reference group), 5-aminosalicylic acid (5-ASA)/sulfasalazine, steroids, and azathioprine (AZA)/6-mercaptopurine (6-MP). We used logistic regression analyses to estimate the relative risk of birth outcomes with 95% confidence intervals. We used a proxy measure for disease activity.
Results: Preterm births were more prevalent among steroid- and AZA/6-MP-exposed women (12.3% and 25%, respectively) compared with the reference group (6.5%). CAs were more prevalent among AZA/6-MP-exposed compared with reference group (15.4%vs 5.7%). Among steroid exposed, the risk of preterm birth was 1.4 (95% CI 0.6-3.3). Among AZA/6-MP exposed, the risk of preterm birth and CAs was 4.2 (95% CI 1.4-12.5) and 2.9 (95% CI 0.9-8.9), respectively.
Conclusions: The relative risk of adverse birth outcomes among CD women varied by type of drugs prescribed during pregnancy. The risk of preterm birth and CAs was greater when AZA/6-MP was prescribed, even after adjusting for confounders. However, further information is needed to determine whether the associations are causal.