The average age of first-time mothers in the U.S. jumped from 21.4 in 1970 to 25 in 2006, an increase of 3.6 years, according to a report in the August edition of NCHS Data Brief, a publication of the CDC's National Center for Health Statistics.
By comparison, the average age at first birth in Switzerland is 29.4 and in Japan is 29.2.
One explanation of the change in average age of first-time mothers is that the proportion of first births to women 35 and older has increased nearly eight times since 1970, the researchers say.
Researchers T.J. Mathews, MS, and Brady E. Hamilton, PhD, both of the National Center for Health Statistics, say average age at first birth is important because it influences the total number of children a woman might have as well as the population's size and future growth. A mother's age is also a factor in birth outcomes such as birth weight and birth defects.
The study also shows:
• The average age at first birth has risen five years or more in Washington, D.C., Massachusetts, and New Hampshire, while increasing less than 2.5 years in Mississippi, New Mexico, and Oklahoma.
• Since 1990, average age at first birth has increased across all racial and ethnic groups.
• Asian or Pacific Islander women had the oldest average age at first birth, at 28.5, and American Indian or Alaska Native women the youngest at 21.9.
• In 1970, average age at first birth was lowest in Arkansas at 20.2 and highest at 22.5 in Connecticut, Massachusetts, and New York. In 2006, Mississippi had the lowest average age at 22.6 and Massachusetts the highest, 27.7.
• The average for non-Hispanic white women was higher at 26 than for the U.S. population as a whole, 25. The average for non-Hispanic black women was 22.7 and the average for Hispanic women was 23.1.
By Bill Hendrick
Reviewed by Louise Chang, MD
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