Lay Summary

Proposal No. IBD-0204R2
Principal Investigator:  Scott M. Montgomery, Ph.D.
Applicant Organization:  Karolinska Institutet (Stockholm, Sweden)
Project Title:  Markers of perinatal bowel colonization and pediatric Crohn's disease risk
Period of Award:  September 1, 2007 – February 28, 2009

The immune system in people with Crohn’s disease overreacts to the presence of microbes that normally inhabit the intestines. As a baby grows, its immune system develops and learns to recognize which microbes in the intestine to ignore and which it should attack: early contact with microbes is likely to be important in this learning process. During a normal pregnancy, the baby is in a relatively sterile environment. The first major contact with microbes occurs when the baby is being born: microbes from the mother begin to colonize the baby’s intestine. After birth, a variety of factors influence which microbes inhabit the baby’s intestine, including use of antibiotics in early life. In this study, the hypothesis is that factors preventing microbial colonizing the baby’s intestine may increase the risk for Crohn’s disease. There is evidence that birth is a critical time when colonizing microbes interact with the immune system. What is likely to prevent microbial colonization of a baby’s intestine? The first important exposure occurs during vaginal birth, but caesarean section may prevent early colonization.

This project will make use of the rich research resources available through routinely collected information in Sweden. Information on individuals can be linked and family members can be identified through the unique identification number assigned to all Swedish residents. Such epidemiological research is possible without revealing the identities of individuals, as the information is supplied to researchers as anonymized data. This study will be able examine reliable and detailed information on the pregnancy and delivery of children with and without pediatric Crohn’s disease, as well as the illnesses (indicating antibiotic treatment) these children had in their first years of life.

This study is unusual in being able to use such accurate and detailed measures of what happened to children when they are so young, but with follow-up to the time when Crohn’s disease is diagnosed in later childhood, usually over ten years later. This study will identify risks for Crohn’s disease during the crucial period when the immune system is developing, thus identifying important targets for further research. If factors such as birth by caesarean section are identified as risks for Crohn’s disease then strategies can be developed to reduce the risk of future Crohn’s disease in infants: such strategies may be particularly relevant for families with a history of inflammatory bowel disease.