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msnbc.com contributor
updated 4/1/2011 12:33:12 PM ET 2011-04-01T16:33:12

One in five of all American moms have kids who have different birth fathers, a new study shows. And when researchers look only at moms with two or more kids, that figure is even higher: 28 percent have kids with at least two different men.

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“To put it in perspective, this is similar to the number of American adults with a college degree,” says the study’s author, Cassandra Dorius, a postdoctoral fellow at the University of Michigan Institute for Social Research. “It’s pervasive.”

Dorius’ study, which was presented Friday at the annual meeting of the Population Association of America, examined data from nearly 4,000 U.S. women who had been interviewed more than 20 times over a 27-year period.

This phenomenon is important to study, Dorius says, because there are consequences to both the mom and her children. Women with children from multiple fathers tend to be disadvantaged compared to other moms. “They are more likely to be under-employed, to have lower incomes, and to be less educated,” Dorius says.

Further, this type of family structure can lead to a lot more stress for everyone involved, in part because the women need to juggle the demands and needs of more than one dad. 

Commentary: 'Baby daddy' study may draw unfair spotlight on black women

“Everyday decisions are more complex and family rules are more ambiguous,” Dorius says. “Families need to figure out who lives with whom and when, who pays for things like clothing, who is responsible for child support.”

Earlier studies that looked at women with children from different dads focused only on young or inner-city mothers.

The new data, pulled from the National Longitudinal Survey of Youth, shows that this kind of family structure is found at all levels of income and education. And it’s frequently tied to divorce and remarriage, not just to single motherhood, Dorius says. Forty-three percent of the women with kids with multiple dads were married when their first babies were born.

Dorius found that a multiple-father type of family structure was more common among minority women, with 59 percent of African-American mothers, 35 percent of Hispanic mothers and 22 percent of white mothers reporting children with more than one father.

Women with low income and little education were also more likely to have children with different birth fathers.

An important message that doesn’t appear to be getting through is just how hard it is to raise a child as a single parent.

"While these women tended to be poorer than others to begin with, their whole lifetimes continue to be disadvantaged," she said.

Dorius’ findings dovetail with some other recent research, says Katherine Stamps Mitchell, an assistant professor of human ecology and sociology at Louisiana State University in Baton Rouge.

Studies have shown that, increasingly, young women are choosing to become moms before they are committing to marriage, Mitchell says.

What we don’t yet know is the long-term impact of that choice on the kids and the moms, Mitchell says.

“This area of research is pretty new,” she adds. “It’s possible that some of these kids will be multiply disadvantaged.”

Mitchell suspects that women would be less likely to choose early and single motherhood if they thought they would have more options in the future.

“Certainly we know that women with higher education are delaying both marriage and childbearing for their careers,” she says. “Women with lower expectations for education and career don’t see that they will be in a significantly different place in 10 years. So there’s no reason to wait to have kids.”

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