Fewer teen moms could help slow U.S. population growth


More women are waiting longer to have kids, according to new analysis of a decades-long trend that could signal a slowdown in the U.S. population growth.

A mother’s average age at the time she gives birth to her first child climbed from 24.9 years to 26.3 years during the period of 2000 to 2014, according to a report released today from the Centers for Disease Control and Prevention. In fact, there was a steeper climb between 2009 and 2014.

Average age of all mothers at childbirth
  First Birth

Source: Centers for Disease Control and Prevention

One big reason is that fewer women under the age of 20 are becoming moms.

One out of seven first births are to teen mothers, a 42 percent drop from 2000, when a quarter of all first-time births were to young mothers, explained T.J. Mathews, a demographer with the CDC who has studied trends like this for two decades.

“It’s not just more women delaying, it’s fewer younger women having that first birth,” Mathews said, resulting in the average age going up. “They’re just not a part of the math anymore.”

By comparison, in 1970 a mother’s average age when she gave birth to her first child was 21.4 years.

This latest trend is reflected in women from all race and ethnic groups and in every state, Mathews said.

“There’s nowhere it’s not happening,” he said. “It’s just happening more in some places.”

Waiting to have kids later in life also narrows the window of time when a woman can give birth overall, he said. That means fewer babies likely will be born, and the population growth rate could slide.

Today, the U.S. breaks even, said Mathews, roughly replacing each person who dies with the birth of a new baby or an immigrant’s arrival in this country.

When those numbers skew dramatically one way or another, problems often arise. For example, Japan’s fertility rate sank to a record low in 2014. Ultimately, that meant Japan’s economy had fewer workers and more aging people who needed care.

Social science suggests a few reasons for why more women wait to have kids. One reason, according to a 2010 study from the Pew Research Center, could include the fact that more women are choosing to pursue college degrees.

For this study, researchers analyzed birth data from the National Vital Statistics System from the CDC’s National Center for Health Statistics. Data included the age of mothers at the time of their first, second, third, fourth and fifth births.

Megan Crigger designed the chart for this post.