Non-Hispanic white children now make up the minority of babies born in the US for the first time, according to latest census estimates, highlighting demographic changes that could reshape US government policy.

Preliminary census estimates also show the share of African-American households headed by women – comprised mostly single mothers – now exceeds African-American households with married couples.

The findings offer a preview of final 2010 census results, released this summer, that provide detailed household breakdowns by age, race and relationship.

Demographers say the numbers provide the clearest indication yet that non-white minority groups will become the majority in the US by the middle of the century.

Currently non-Hispanic white children make up just under half of all three-year-olds in the US, the youngest age group shown. In 1990 the proportion was more than 60%.

Demographer William Frey from the Brookings Institution, which analysed the data, said the data released so far suggested minorities already outnumber whites among babies under two.

By contrast non-Hispanic white people make up the vast majority of older Americans – 80% of the over 65s and 73% of those between 45 and 64.

"The recent emergence of this cultural generation gap in states with fast growth of young Hispanics has spurred heated discussions around immigration and the use of government services," Frey said. "But the new census makes plain that our future labour force is absolutely dependent on our ability to integrate and educate a new diverse child population."

Kenneth Johnson, a sociology professor and senior demographer at the University of New Hampshire, noted much of the change is being driven by increases in younger Hispanic women having more children than non-Hispanic white women.

The census figures come amid heated debate on a number of controversial issues including immigration, gay marriage and the rising cost of welfare benefits.

Alabama became the latest state this month to pass a wide-ranging anti-immigration law which requires schools to report their students' immigration status to the authorities. This follows tough immigration measures passed in similarly Republican-leaning states such as Georgia, Arizona and South Carolina.

But Massachusetts, New York and Illinois have all opted out of a federal plan to deport criminals who are not US citizens, saying it has made illegal immigrants afraid of reporting crimes to police. California may also opt out.