As American women continue to delay parenthood, rates of teenage births and births for women in their early 20s are at all-time lows, federal health officials reported Friday.
U.S. women have their first baby at age 25.6 on average, according to 2011 figures released by the U.S. Centers for Disease Control and Prevention (CDC). This is up slightly from 2010 and significantly older than the 1970 average of 21.4 years.
Births to girls 15 to 19 declined 8 percent between 2010 and 2011, and births to women 20 to 24 years old dropped 3 percent to a record low, the CDC report stated.
"If this [trend] results in more births being planned and intended it is difficult to object to it," said Dr. Jeffrey Ecker, director of Obstetrical Clinical Research and Quality Assurance at Massachusetts General Hospital in Boston.
"If we are talking about a shift from early 20s to late 20s or early 30s, the expectation is that outcomes would be safe and healthy. The message isn't that it's fine to wait until a woman is in her late 30s or 40s to think about becoming pregnant," added Ecker, who is also chair of the American College of Obstetricians and Gynecologists' Committee on Obstetric Practice.
As women get older it is more difficult to become pregnant, Ecker said, adding that the likelihood of miscarriage and other complications also increases.
Overall, 3.9 million U.S. births were reported in 2011, representing the lowest general birth rate since 1998 -- 63.2 births per 1,000 women aged 15 to 44 -- and 1 percent less than in 2010, the CDC reported.
Birth rates were unchanged for women aged 30 to 34 but rose for women 35 to 44.
Births to unmarried women declined in 2011 for the third year in a row -- down another 2 percent from 2010.
Experts found good news in the report.
In terms of health, highlights are a leveling off of cesarean births and the continued decline in the preterm birth rate, said lead author Joyce Martin, an epidemiologist at CDC's National Center for Health Statistics, Division of Vital Statistics, Reproductive Statistics.
In 2011 the rate of cesarean delivery remained about the same as the year before -- nearly 33 percent of all births. Previously, the number of women undergoing C-sections had increased steadily, jumping 60 percent from 1996 to 2009.
Meanwhile, the rate of preterm deliveries (before 37 weeks) dropped in 2011 for the fifth straight year to 11.7 percent of all births, down 2 percent from 2010 and 8 percent from its high in 2006.
The rate of babies born at a low birth weight in 2011 was 8.10 percent -- down somewhat from 8.15 percent in 2010 and 2 percent lower than the 2006 peak of 8.26 percent.
Other notable findings: Multiple births were relatively unchanged in recent years. Twins accounted for 33.2 per 1,000 total births in 2011.
Births of triplets and more also remained unchanged at 137 per 100,000.
Dr. Mitchell Maiman, chairman of obstetrics and gynecology at Staten Island University Hospital in New York City, said he expects that women will continue to postpone childbirth.
"More and more women are not only in the workforce, but more women are the primary breadwinner in the family," he said.
"So you are going to have more women who are delaying childbearing to enhance their careers. And you have amazing technology to enable them to accomplish that," Maiman said. "You are going to see older and older mothers."