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. Hospital discharge data was used 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 these findings support the notion that circumcision may protect boys from UTI, the magnitude of this effect may be less than previously estimated.