Paternal age and the risk of birth defects in Norway

Purpose We studied 1,869,388 births from The Medical Birth Registry of Norway to assess the effect of fatherʹs age on risks of birth defects in offspring. Method Thirteen separate categories were studied including pooled categories of neural tube defects and any type of defect. We used logistic regression models to adjust for maternal age, year of birth, maternity institution, parity, and correlation between siblings. Results There was little evidence of increased risk by high paternal age for any category of defects, except for a category of “other central nervous system” where risk estimates were 2.5-fold (95% CI: 1.2–5.5) for fathers aged between 45 and 49 years compared with the reference age group (25–29 years). The risk for neural tube defects was 1.3-fold (95% CI: 1.1–1.5) when the father was aged between 20 and 24 years relative to the reference. A pattern of moderately higher risks for younger fathers was consistent for anencephaly and spina bifida. Increased risk of heart defects was also estimated among children of young fathers. Conclusions This study does not show consistent evidence that paternal ageing is a risk for birth defects among offspring. Low paternal age, or factors associated with younger parents, may however be associated with increased risk of neural tube defects in their offspring.