The birth rate from mothers in their teens and early twenties has never been lower in America, as young women continue to delay family life into later years.

American women birth their first baby at age 25.6 years on average, according to the U.S. Centers for Disease Control and Prevention. Although slightly higher than the previous year, the 2011 numbers represent a significant jump in age from 1970, when the average first-time mother was 21.4 years of age.

Births from mothers aged 15-19 fell by 8 percent between 2010 and 2011 while births from mothers 20-24 years of age dropped 3 percent to an all-time low.

"If this results in more births being planned and intended it is difficult to object to it," Dr. Jeffrey Ecker, director of obstetrical clinical research and quality assurance at Massachusetts General Hospital, told reporters.

However, the general trend doesn't represent wonderful news to all thirty-something women who've delayed childbirth until later in their fertile years. "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," Ecker said.

Also the chairman of the American College of Obstetricians and Gynecologists' committee on obstetric practice, Ecker noted that older women experienced greater chances of miscarriages and other pregnancy complications.

In total, American women gave birth to 3.9 million babies in 2011 in the lowest yearly birth cohort since 1998, at 63.2 births per 1,000 women aged 15-44 — a slight drop from 2010, according to the CDC. While birth rates remained static for women in their early thirties, more women in their mid-thirties to mid-forties gave birth.

For better or worse, births to unmarried women fell in 2011 for the third year in a row, declining another 2 percent from 2010.

However, the health of the mothers and babies in the smaller 2011 cohort was generally improved, across a number of measurements. The rate of Cesarean delivery remained steady at nearly one in three births, stabilizing after a 60 percent jump from 1996 to 2009. Also, the rate of premature babies, those born before 37 weeks of gestation, dropped for the fifth straight year to 11.7 percent of births, down 8 percent from 2006.

Experts say women will continue to delay childbirth to advance careers, coming to term with pregnancy later and later in life.