Objective: To confirm or refute a possible association of parenteral vitamin K prophylaxis and childhood cancer.

Design: Population based case-control study in Lower Saxony: children with leukaemia or other tumours versus two control groups.

Subjects: 272 cases with leukaemia or other common tumors and ages at diagnoses >30 days and <15 years. 334 population based controls without diagnoses of cancer matched to the leukaemia cases for age and sex.

Main exposures: i.m or s.c. vitamin K prophylaxis vs oral or none.

Results: An association between parenteral vitamin K exposure and childhood cancer (leukaemias and other tumours combined) could not be confirmed (OR 1.04, 90% CI 0.78-1.40). For leukaemias the observed odds ratio was only 0.98 (90% CI 0.68-1.40) These odds ratios remained almost unchanged with several potential confounders in the logistic regression model.

Conclusions: This population based study adds substantial evidence that there is no association between parenteral vitamin K and childhood cancer.