Cohort study on circumcision of newborn boys and subsequent risk of urinary-tract infection

Background A decrease in risk of urinary-tract infection is one of the most commonly given reasons for circumcision of newborn boys. Previous studies have reported rates of UTI to be 10-20 times higher in uncircumcised than i n circumcised boys. This population-based cohort study followed neonates in Ontario, Canada, prospectively to study the relation between circumcision and subsequent UTI risk. Methods Eligible boys were born to residents of Ontario between April 1, 19 93, and March 31, 1994. We used hospital discharge data to follow up boys u ntil March 31; 1996. Findings Of 69100 eligible boys, 30105 (43.6%) were circumcised and 38995 ( 56.4%) uncircumcised. 888 boys circumcised after the first month of life we re excluded. 29217 uncircumcised boys were matched to the remaining circumc ised boys by date of birth. The 1-year probabilities of hospital admission for UTI were 1.88 per 1000 person-years of observation (83 cases up to end of follow-up) in the circumcised cohort and 7.02 per 1000 person-years (247 cases up to end of follow-up) in the uncircumcised cohort (p < 0.0001). Th e estimated relative risk of admission for UTI by first-year follow-up indi cated a significantly higher risk for uncircumcised boys than for circumcis ed boys (3.7 [2.8-4.9]). 195 circumcisions would be needed to prevent one h ospital admission for UTI in the first year of life. Interpretation Although our findings support the notion that circumcision m ay protect boys from UTI, the magnitude of this effect may be less than pre viously estimated.