Objectives To investigate perinatal risk factors for testicular cancer in a Northern Ireland population cohort.

Methods Perinatal data have been routinely recorded in Northern Ireland for all births in the period 1971–1986 (n=447, 663). Testicular cancer status was ascertained in this cohort by identifying 249 individuals diagnosed from 1971 to 2008 and date of birth in the period 1971–1986.

Results Increased testicular cancer risk was associated with higher maternal age (>35 years), lower birth weight (<2500 g), caesarean delivery, decreased birth order and lower socio-economic status. Following multivariable analyses, the association between higher maternal age and testicuar cancer risk remained significant (OR 1.55; 95% CI 1.07 to 2.25). Caesarean delivery was also associated with a significant increase in the risk of testicular cancer (OR 1.65; 95% CI 1.11 to 2.44). Increasing birth order was associated with a significant decrease in the testicular cancer risk (OR 0.59; 95% CI 0.41 to 0.83) comparing birth order three or more with the firstborn.

Conclusion These findings demonstrate that maternal age at delivery, birth order and mode of delivery are significantly associated with testicular cancer risk. These associations may be due to earlier exposure to infectious agents or increased immune modulation.