OF COURSE, 2007 was a year in which more babies were born in the United States than any other year in the nation's history. In the past, a fluctuation of births by 1 or 2 per cent would not be seen as very significant, especially from such an unusual year.

But the drop seems to break an unusual trend. Births had been rising since 2002, and birth rates had been increasing in women of different age groups, said Ms Ventura, chief of the agency's reproductive statistics branch.

The new report is an early count of births from each state, and does not contain demographic breakdowns that might more completely explain whether birth declines occurred in some groups, but not others.

While the recession probably played an important role in fewer babies, another factor may be the net decline in recent years in immigration to the United States, said Mark Mather, demographer with the Population Reference Bureau.

'If there are fewer immigrants coming to the US, there are fewer mums and dads,' said Mr Mather, noting that California and Florida are states with large immigrant populations.

'I don't think we have enough data to know for sure what's going on,' he added.

About half of US pregnancies are unplanned. But Prof Hogue said the recession likely affected the other half.

The recession also may have cut into the number of unplanned pregnancies that progressed to live births, but it's hard to say.

Abortion statistics for 2008 are not yet available, Prof Hogue said. -- AP