For the first time, ethnic minorities make up a majority of babies in the United States, official figures show.
The change reflects a growing age divide between mostly white, older Americans and predominantly minority youths that could reshape government policies.
Preliminary census estimates also show the share of African-American households headed by women - made up of mostly single mothers - now exceeds African-American households with married couples, a sign of declining US marriages overall but also continuing challenges for black youths without involved fathers.
The findings, based on the latest government data, offer a preview of final 2010 census results being released this summer that provide detailed breakdowns by age, race and householder relationships such as same-sex couples.
Demographers say the numbers provide the clearest confirmation yet of a changing social order, one in which racial and ethnic minorities will become the US majority by the middle of the century.
Currently, non-Hispanic whites make up just under half of all three-year-olds, which is the youngest age group shown in the Census Bureau's October 2009 annual survey, its most recent. In 1990, more than 60% of children in that age group were white.
The preliminary figures are based on an analysis of the Current Population Survey as well as the 2009 American Community Survey, which sampled three million US households to determine that whites made up 51% of babies younger than two.
After taking into account a larger-than-expected jump in the minority child population in the 2010 census, the share of white babies falls below 50%.
By contrast, whites make up the vast majority of older Americans - 80% of the over-65s and roughly 73% of people aged 45-64.
Kenneth Johnson, a sociology professor and senior demographer at the University of New Hampshire, noted that much of the race change is being driven by increases in younger Hispanic women having more children than white women, who have lower birth rates and as a group are moving beyond their prime childbearing years.