Fewer than four million births were counted last year - the lowest number since 1998.
The flagging economy has been seen as the primary explanation. The theory is that many women or couples who are out of work, underemployed, or have other money problems feel they can't afford to start a family or add to it.
The economy officially was in a recession from December 2007 until June 2009. But well into 2011, polls show most Americans remained gloomy.
The report by the Centers for Disease Control and Prevention is a first glimpse at 2011 birth certificate data from state health departments.
Key findings include:
The birthrate for Hispanic women dropped 6 percent. It declined 2 percent for black women, stayed the same for whites, and actually rose a bit for Asian American and Pacific Islanders.
Birthrates fell again for women in their early 20s, down 5 percent from 2010 - the lowest mark for women in that age group since 1940, when comprehensive national birth records were first compiled.
Birthrates for teen mothers have been falling since 1991 and hit another historic low. The number of teen births last year - about 330,000 - was the fewest in one year since 1946. The teen birthrate fell 8 percent, and at 31 per 1,000 girls ages 15 through 19 was the lowest in more than seven decades.
The report also noted a fourth straight decline in a calculation of how many children women have over their lifetimes, based on the birthrates of a given year.
A rate of a little more than 2 children per woman means each couple is helping keep the population stable. The U.S. rate last year was slightly below 1.9.
Countries with rates close to 1 - such as Japan and Italy - face future labor shortages and eroding tax bases as they fail to reproduce enough to take care of their aging elders.
