American women are waiting longer than ever to become mothers

More and more women in the United States are waiting until they're older to start having children.

The average age of women having their first child was a record high of 26 years old in 2013, according to the Centers for Disease Control and Prevention's National Vital Statistics Report.

That's an increase of 3.3 years since 1980, when the average age was 22.7.

The average age of first-time mothers is increasing because more women are waiting until their 30s and 40s to start having kids and fewer women are having their first kids in their teens and 20s, the CDC report says.

Since 1980, birth rates to women over 30 have been rising steadily, particularly in the 30-34 age group (the red line on the graph below). Birth rates for women ages 25-29 are not that different than in 1980, but rates for teens and women in their early 20s have dropped dramatically (as shown by the green and purple lines).

The majority of births are still to women under 35, about 85% of the total in 2013.

The CDC report says the increase in births to women over 35 has been linked to the use of fertility treatments and therapies, which can mean anything from talking to a doctor to doing in-vitro fertilization.

That makes sense, because a woman's fertility declines with age as her eggs accumulate abnormalities that make them less likely to develop into healthy babies if fertilized. But with more technologies on the horizon that might eventually offer older women increased chances of getting pregnant, it's possible the average age of women becoming mother for the first time will just keep going up.