Older Fathers May Determine Health of the Baby More Than Moms Do, Study Shows

Fathers have more of a role in their child's genetic makeup than you might think. ROBIN VAN LONKHUIJSEN/AFP/Getty Images

It's time we stop blaming mom for all our own shortcomings. New research suggests that fathers may contribute more genetic mutations than mothers to their children, especially if the dads are older.

A study published Wednesday in Nature revealed that as we age, we pass on more genetic mutations to our offspring, but older fathers can pass on up to four times as many new genetic mutations to their children than age-matched mothers.

Related: Waiting to have kids? Older dads have geeky sons with higher IQs

The study looked specifically at de novo, or new, mutations. These mutations are present for the first time in a family due to a variation that occurred in either the egg or sperm cell. They can be passed onto the children, but are not seen in the parents.

In the study, Kari Stefansson, CEO of deCODE, and his team used genetic data from 14,000 people in Iceland, including 1,500 sets of parents and children. Results showed that men passed on one new mutation for every eight months of age. By comparison, women passed on one new mutation for every three years of age. Based on these rates, a child born to two 30-year-old parents would inherit an average of 45 new mutations from their father, but only 11 new mutations from their mother, The Guardian reported.

In a statement, Stefansson explained that new mutations are crucial for evolution because they launch "a constant flow of new versions of the human genome into the environment." However, said Stefansson, such mutations, "are also believed to be responsible for the majority of cases of rare diseases of childhood."

Related: Should men worry about their own biological clock?

Parents are often concerned about how maternal age affects fertility, but this new study adds to a growing pool of research that suggests a father's age at conception also contributes to a child's future health. For example, a study published this May in The Journal of the American Academy of Child and Adolescent Psychiatry found evidence to suggest that children born to fathers aged 51 and older were more likely to socially lag behind their peers with younger fathers. However, children born to fathers aged 25 and under also experienced similar social delays, so it's best to take the older-father findings with a bit of skepticism.

The Centers for Disease Control and Prevention report that American couples are waiting longer than ever to start their families. Studies like this new one from Nature could raise concerns about doing so.