Background: Early life factors have been postulated to play a role in development of immune tolerance and intestinal microbiome, which in turn may influence the risk of inflammatory bowel disease.
Methods: We conducted a prospective cohort study of 60,186 U.S. women enrolled since 1976 in the Nurses Health Study (NHS) I and 86,495 women enrolled since 1989 in the NHS II with no history of ulcerative colitis (UC) or Crohn's disease (CD). Information about breastfeeding, birth weight, and preterm birth were collected in 1992 in NHS I and 1991 in NHS II. Diagnoses of CD and UC were confirmed through review of medical records. We used Cox proportional hazards models to calculate hazard ratios and 95% confidence intervals.
Results: Among 146,681 women over 3,373,726 person-years of follow-up, we documented 248 cases of CD and 304 cases of UC through 2007 in NHS II and 2008 in NHS I. The median age of diagnosis was 51 for CD and 49 for UC. Compared with women who were not breastfed, women who were breastfed had multivariate-adjusted hazard ratios of 0.99 (95% confidence interval, 0.76-1.30) for CD and 1.03 (95% confidence interval, 0.81-1.32) for UC. Similarly, low or high birth weight and preterm birth were not significantly associated with risk of UC or CD.
Conclusions: In 2 large prospective cohorts of U.S. women, we did not observe a significant association between early life factors including having been breastfed, birth weight, preterm birth, and risk of adult-onset UC and CD.