Pyloric stenosis occurs in 0.24 percent of white live births, in 0.18 percent of Hispanic births, in 0.07 percent of black births and in 0.06 percent of Asian births, according to Medscape. It is less common in mixed-race births and four times more common in males than in females.
Pyloric stenosis is most common in first-born male children of northern European ancestry. Bottle feeding may increase the risk of pyloric stenosis, and a strong association exists with macrolide antibiotic treatment in infants, reports Medscape. Symptoms of pyloric stenosis appear within three to six weeks of birth. It rarely occurs in children older than 3 months, according to Mayo Clinic.