Infantile hypertrophic pyloric stenosis (IHPS) is the most common condition requiring surgery in the first few months of life. It is characterized by hypertrophy of the circular muscle of the pylorus, causing pyloric channel narrowing and elongation. The incidence of IHPS varies widely with geographic location, season, and ethnic origin.1 The incidence has been reported to be approximately 0.5–2 per 1000 live births.2 4 A remarkable decline in the incidence of IHPS has been reported during the 1990s and early 2000s in Western countries.2 , 3 Environmental changes rather than genetic ones are likely to explain this development (e.g., increased breastfeeding rate).3 , 5 Boys are affected five times more often than girls, and the ratio of affected boys to girls was relatively constant throughout the past decades.2