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 in 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, 1993, and March 31, 1994. We used hospital discharge data to follow up boys until March 31, 1996. Findings Of 69 100 eligible boys, 30 105 (43·6%) were circumcised and 38 995 (56·4%) uncircumcised. 888 boys circumcised after the first month of life were excluded. 29 217 uncircumcised boys were matched to the remaining circumcised 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). The estimated relative risk of admission for UTI by first-year follow-up indicated a significantly higher risk for uncircumcised boys than for circumcised boys (3·7 [2·8–4·9]). 195 circumcisions would be needed to prevent one hospital admission for UTI in the first year of life. Interpretation Although our findings support the notion that circumcision may protect boys from UTI, the magnitude of this effect may be less than previously estimated.