PhotoDeciding to start a family is a big decision, but one that many consumers have embraced at a young age in the past. However, recent research shows that prospective parents are now waiting a little longer to have kids.

A new study from Stanford University shows that fathers of newborns are 3.5 years older on average when compared to four decades ago, with men over 40 accounting for 9% of all U.S. births. The researchers attribute the shift to changing social roles and advances in contraception.

"We've seen a lot of changes in the last several decades. Contraception is more reliable and widespread. Women have become more integrated into the workforce. This seems to be reflected in an increasing parity in parental ages over the last four decades," said senior author Dr. Michael Eisenberg.

Parents waiting to have kids

The researchers came to their conclusions after analyzing data from the National Vital Statistics System, which tracked all 168,867,480 U.S. live births from 1972 to 2015.

Among the findings, the researchers say that the average paternal age when a child was born increased from 27.4 years to 30.9 years over the study period. Asian-American fathers from Japanese and Vietnamese backgrounds were the oldest on average when having a child, at just over 36 years old. Fathers with higher levels of education also tended to be older when they had their first newborn, at 33.3 years old.

Over the same time period, the researchers say that the percentage of newborns’ fathers over the age of 40 more than doubled, from 4.1% to 8.9%, while those over the age of 50 increased from 0.5% to 0.9%.

Of course, fathers haven’t been the only ones waiting to have children. In fact, Eisenberg points out that maternal ages at birth have advanced even more than paternal ages in the same timeframe.

“This may be a consequence of women waiting longer to get married or putting off childbearing as the years they spend in higher education increase and as careers become more central to their lives,” he said. “The result is that the average age difference between moms and dads has been shrinking, from 2.7 years in 1972 to 2.3 years in 2015."

The risks of waiting

While waiting longer to have children may be beneficial for some couples, the researchers point out that there are some inherent risks involved.

"Every potential dad acquires an average of two new mutations in his sperm each year. And there are associations between older fatherhood and higher rates of autism, schizophrenia, chromosomal abnormalities, some pediatric cancers and certain rare genetic conditions," said Eisenberg.

The researchers say that putting off having kids also holds negative implications for the economy. "Fewer people being born means fewer productive workers a generation down the road," Eisenberg added. "This can obviously have profound tax and economic implications.”

The full study has been published in Human Reproduction.


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