USA Today reports on new numbers released from the National Center for Health Statistics, indicating that 2007 set an all-time record for births in the United States, with some interesting changes in the motherhood landscape.

The USA’s banner year for babies in 2007 set a record of 4.31 million — and was driven in large part by growing numbers of unmarried adult women giving birth, new government data show. Childbearing by unmarried women reached “historic levels,” the report says, to an estimated 1.7 million, or 40% of all births. There were increases in the birth rate and the proportion of births as well as an increase in the number. Teen moms accounted for 23%. The report, based on preliminary data, was released Wednesday by the National Center for Health Statistics.

Since 2002, all measures of childbearing by unmarried women have been “climbing steeply,” says Stephanie Ventura, a demographer who worked on the government report, which is based on birth certificates. The report found 60% of women 20-24 who had babies in 2007 were unmarried, up from 51.6% in 2002. Among ages 25-29, 32.2% of births were to unmarried women, vs. 25% in 2002. For ages 15-19, almost 86% were unmarried, compared with 80% in ’02.

But what about the number of births we can expect during the recession? Call in the sociologist!

Evidence from the Depression and past recessions has shown that numbers of births fall in hard economic times.

But University of Chicago economist and sociologist Gary Becker says that may not hold true anymore, with greater numbers of women in the labor force. Women laid off from their jobs might see unemployment as the time to have a child, he says: “Births might go up during recession.”

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