Original article—alimentary tract
Crohn's Disease Is a Risk Factor for Preterm Birth

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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.

Section snippets

Study Population

We conducted this prevalence study in Sweden and Denmark, whose combined population is more than 14 million inhabitants. All residents of both countries receive free tax-supported medical care. Our study population included all primiparous women in both countries with a singleton live birth or a stillbirth. The women were identified through medical birth registries. The study period commenced in 1994 (when Denmark's National Patient Registry changed its coding to the International

Results

During the 1994–2006 study period 2377 singleton births occurred among primiparous women diagnosed with CD and 869,202 singleton births occurred among primiparous women with no CD diagnosis. By country, 60.2% of the births took place in Sweden and 39.8% in Denmark. Compared with women without CD, women with CD were generally of higher maternal age and more likely to be cigarette smokers. The 2 groups did not differ in the proportion living with the baby's father. Women with CD were more likely

Discussion

In this large population-based study, we found that primiparous women with CD were at increased risk of preterm delivery and cesarean section. Risk for growth restriction measured as SGA at birth was slightly elevated, especially during the latest time period. There was no association between maternal CD and overall or specific congenital malformations, risk for low 5-minute Apgar scores, pre-eclampsia, and stillbirth. Adverse birth outcome appeared to be correlated with severity of CD, as

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    Conflicts of interest The authors disclose the following: The Department of Clinical Epidemiology, Aarhus University Hospital and the Clinical Epidemiology Unit, Karolinska Institutet, are involved in pharmacoepidemiological studies, including studies on drugs used for treatment of IBD. These studies are funded by research grants from several pharmaceutical companies (Amgen, Pfizer, Glaxo, and Centocor).

    Funding The study was supported by a postdoctoral scholarship awarded to Olof Stephansson by the Swedish Society of Medicine and by funding from Klinisk Epidemiologisk Forskningsfond at Aarhus University, Denmark.

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