Crohn's disease is a risk factor for preterm birth

Background & aims: Women with Crohn's disease (CD) are considered to be at increased risk for adverse outcomes of pregnancy. However, the few studies assessing this risk have had small sample sizes and limitations. We examined outcomes of pregnancy among a large cohort of primiparous women with CD.

Methods: Our population-based prevalence study utilized data from medical birth registries in Sweden and Denmark between 1994 and 2006. Linking birth registry data with national patient registries, we identified 2377 women with a hospital diagnosis of CD prior to delivery and 869,202 women with no diagnosis of CD. Using logistic regression analysis, we estimated relative risks with 95% confidence intervals (CI) for pre-eclampsia, preterm birth, 5-minute Apgar scores below 7, cesarean section, small for gestational age (SGA), stillbirth, and congenital malformations.

Results: Maternal CD was associated with increased risk of moderately and very preterm birth (prevalence odds ratio [POR], 1.76; 95% CI, 1.51-2.05; and POR, 1.86; 95% CI, 1.38-2.52, respectively). Maternal CD was also associated with increased risk for cesarean section (POR, 1.93; 95% CI, 1.76-2.12). The strongest associations with CD were observed for prelabor cesarean section and induced preterm delivery. Risk of small size for gestational age birth was slightly increased among women with CD, especially during the time period of 2002-2006 (POR, 1.43; 95% CI, 1.09-1.89). We found no increased risks for pre-eclampsia, low 5-minute Apgar score, stillbirth, or congenital malformations.

Conclusions: Maternal CD is a risk factor for preterm birth, but not birth defects.