Study: 1 in 7 U.S. Babies Born to Moms 35+

While most women giving birth are doing it within the context of marriage, researchers said a record 41 percent of births were to unmarried women in 2008. That's up from 28 percent in 1990, according to the study, "The New Demography of American Motherhood." The trend crossed major racial and ethnic groups.

Nearly 14 percent of mothers of newborns were 35 or older two years ago - and only about 10 percent were in their teens. The age trend was reversed in 1990, when teens had a 13 percent share of births.

Today, one in seven babies is born to a mother at least 35 years old. In 1990, one in 11 had a mother in that age group.

Most mothers of newborns (54 percent) had at least some college education in 2008, an increase from 41 percent in 1990. Among mothers 35 or older, 71 percent had at least some college education.