Imperforate anus in 700,000 consecutive liveborn infants.

We have studied the incidence of imperforate anus (anorectal atresia and stenosis) occurring in almost 700,000 consecutive liveborn infants in British Columbia (B.C.) from 1964-1982 using the records of a health surveillance registry which uses multiple sources of ascertainment. The estimated incidence rate was 1 in 2,524 live births (273 cases out of 689,118 consecutive liveborn infants). Data pertaining to sex ratio, additional anomalies, recurrence, and mortality were also analyzed over the period 1952-1983. Additional anomalies were common in infants with anorectal atresia and stenosis; approximately 6 out of 10 cases had anomalies outside the anorectal canal. Skeletal and limb anomalies were frequent, occurring in almost one-third of patients. Also common were genitourinary anomalies, occurring in one-third of patients. Details of associated anomalies occurring in these infants are given, and clinical implications arising from the study regarding the neonatal assessment of infants with imperforate anus are discussed.