Where have all the ‘pyes’ gone?

Have you noticed that there are fewer babies with infantile hypertrophic pyloric stenosis (IHPS) these days? The decreasing prevalence in different countries has been reported several times, including in Archives,1 but the reasons have been unclear. A study from the USA may throw some light on this (JAMA Pediatr. Online 21 October 2013. doi:10.1001/jamapediatrics.2013.2857). McAteer and colleagues from Washington State analysed birth data and linked it to hospital admissions for IHPS (714 infants). As elsewhere, the incidence fell: from 14 per 100 000 births in 2003 to 9 per 100 000 in 2009. Those with IHPS were more likely to have been bottle rather than breast fed after birth (19.5% vs 9.1%; adjusted OR 2.31; 95% CI 1.81 to 2.95). When they adjusted for potential confounding factors they found that baby's gender and maternal smoking made no difference, but increased maternal age and higher parity made the association stronger. Part of the reason for the decline, they conclude, could be that …