Aug. 13 -- WEDNESDAY, Aug. 12 (HealthDay News) -- New mothers are getting older.
In the United States, the average age of women giving birth for the first time rose from 21.4 years in 1970 to 25 in 2006, according to a new report from the National Center for Health Statistics (NCHS).
Births to older women are partly responsible for the upward trend.
"In 1970, just 1 percent, or one in 100, [of] births were to women 35 and over," said study author T.J. Mathews, a demographer with the NCHS, which is part of the U.S. Centers for Disease Control and Prevention. "In 2006, it was one in 12 births. It's a dramatic transition."
On the other hand, the United States still has the youngest age of first-time mothers in the developed countries studied. In Britain, Switzerland and other nations, the average woman now has her first baby at nearly 30 years of age.
"The U.S. is only now caught up to where other countries were in 1970 [for average age of first-time mothers]," Mathews said.
Despite the surge in older moms, a high, but improving, teen birth rate keeps the U.S. figures down.
"We still do have a good number of unplanned and teen pregnancies," said Dr. Jennifer Wu, an obstetrician/gynecologist with Lenox Hill Hospital in New York City.
This new data is somewhat different from past analyses.
"We hadn't really looked at the component of average age of first births," Mathews said. "In the past, we looked at all births."
And first births are an important gauge of future trends, such as how many children a woman has, which affects population, as well as birth weight and birth defects.
The trend toward later motherhood was seen in all racial and ethnic groups and in all states plus the District of Columbia, but some areas saw larger gains than others.
The biggest jumps were 5.5 years in DC, 5.2 years in Massachusetts and 5.1 years in New Hampshire.
New Mexico, Mississippi and Oklahoma had the smallest increases: 2 years, 2.3 years and 2.4 years, respectively.