[Infantile hypertrophic pyloric stenosis. Decreasing incidence].

The aim of this study was to confirm a clinical suspicion that the frequency of this disease is in decline. A retrospective review of case notes of all children admitted and operated in all hospitals in Viborg County during the period of 1.1.1973 to 31.12.1997 was performed. The local survey was supplemented with a national survey. One hundred and forty-seven patients from Viborg County were operated for infantile hypertrophic pyloric stenosis during the period described. Divided into five year periods the number per 1000 living births was consecutively 1.6, 2.4, 2.0, 2.8 and 0.9. The same tendency was found nationally, Table 1. The decrease started in 1993 and has since strengthened. The reason is unknown, but there is a relation regarding to the timing of a change in recommendations concerning positioning of infants during sleep. However, a causal relation is unknown.