Objectives: To investigate an apparent decline in the rate of infantile hypertrophic pyloric stenosis (IHPS) and to examine the characteristics of children with IHPS and any associated malformations.
Design: Cohort study in which children with IHPS were compared with the population of live births. Trends of IHPS were compared in two data sets: a population-based birth defects registry and hospital discharge data.
Participants: Children with IHPS identified from a birth defects registry and the population of live-born infants born to residents of New York State from 1983 to 1990.
Main outcome measure: Trends in the incidence of IHPS in the two data sets, and demographic characteristics and malformations associated with IHPS.
Results: The rate of IHPS declined from 2.4 per 1000 live births in 1984 to 1.7 in 1990. White race and male gender were associated with a higher occurrence of IHPS; high birth order, older maternal age, higher maternal education, and low birth weight were associated with lower occurrence. Seven percent of children with IHPS had a major malformation compared with 3.7% of the general population. Three major malformations occurred more frequently in children with IHPS: intestinal malrotation, obstructive defects of the urinary tract, and esophageal atresia. Fewer cases were found in the birth defects registry than in the hospital discharge data.
Conclusions: Underreporting of IHPS to the birth defects registry accounts for some of the decline. Children with IHPS have more major malformations than the general population, although some of the excess could be attributed to increased detection. Further investigation is needed into the environmental factors, especially socioeconomic, associated with IHPS.