Hypertrophic pyloric stenosis in utero.

Hypertrophic pyloric stenosis (HPS) is the most common surgical condition producing vomiting in infants. It has been reported as early as the 1st week of life. We report an infant with HPS seen on prenatal ultrasound. Although infants with HPS usually present between 3 and 5 weeks of life, HPS must be considered as part of the differential diagnosis of newborns with non-bilious vomiting.