BACKGROUND: The aim of this study was to describe prescription patterns for azathioprine and corticosteroids for pregnant women with inflammatory bowel diseases (IBD) before, during, and after pregnancy and to describe pregnancy outcomes. METHODS: A cohort composed of all singleton pregnancies in Danish registries from 1996 to 2009 was divided by maternal IBD status: Crohn's disease (CD, n = 827), ulcerative colitis (UC, N = 1361), or no IBD diagnosis (background population, n = 814,231). The number of women with a prescription for azathioprine, local and systemic steroids within a 3-month period was computed for each of the pregnancy trimesters and the year before and after pregnancy. Outcomes of interest were stillbirth, perinatal mortality, low birth weight (LBW), preterm birth, and small for gestational age (SGA). RESULTS: Number of prescriptions for azathioprine decreased just before and during pregnancy and increased after birth. Number of prescriptions for local and systemic corticosteroids decreased approximately 30% compared with before pregnancy and increased in the second trimester. There was an increased risk among mothers with IBD of LBW (adjusted odds ratio [adjOR]: CD: 2.25 [95% confidence interval {CI}, 1.74-2.91], UC: 1.81 [95% CI, 1.42-2.30]), preterm birth (adjOR: CD: 2.54 [95% CI, 2.04-3.15], UC: 1.86 [95% CI, 1.52-2.27]), and SGA (adjOR: CD: 1.99 [95% CI, 1.26-3.15], UC: 1.80 [95% CI, 1.18-2.75]). CONCLUSION: Use of azathioprine and corticosteroids was often reduced or discontinued before or during early pregnancy followed by an increased use of corticosteroids later in pregnancy. Women diagnosed with IBD and with prescriptions for azathioprine and/or corticosteroids, have an increased risk of LBW, pre-term birth, and SGA. Birth Defects Research (Part A) 106:494-499, 2016. © 2016 Wiley Periodicals, Inc.