The birthrate among U.S. girls ages 15 to 19 fell from 41.5 to 39.1 births per 1,000 teens – a 6 percent drop to the lowest rate in the nearly 70 years the federal government has been collecting reliable data, according to a preliminary analysis of the latest statistics.

“The decline in teen births is really quite amazing,” said Brady E. Hamilton of the National Center for Health Statistics, who helped perform the analysis…

The reason for the record low remains unclear, but some experts attributed it to the recession, noting that the overall fertility rate as well as the total number of births in the United States fell a second straight year in 2009 as well.