The current evidence does not prove a causal link

The cause of Crohn's disease is likely to be multifactorial, and great interest was generated by two Swedish studies suggesting a high risk of Crohn's disease in those exposed to measles in utero.1 2 The report in this week's issue from Nielsen et al (p 196),3 however, is not alone in suggesting that there is no increased risk.

The two Swedish papers studied largely the same group of patients. Both studies were the result of two index cases of Crohn's disease noted to have been exposed to measles in utero (accounting for two out of four cases in the second study). The first report, in 1994, compared the expected and observed month of birth in patients with Crohn's disease born in 1945-54 in relation to the peak months of measles epidemics. The standardised incidence ratio was 1.46 (95% confidence interval 0.83 to 2.21) for future development of Crohn's disease …