The first national study of the prevalence of multiple partner fertility shows that 28 percent of all U.S. women with two or more children have children by more than one man. The study will be presented April 1 in Washington, D.C., at the annual meeting of the Population Association of America.

“I was surprised at the prevalence,” says demographer Cassandra Dorius, a postdoctoral fellow at the University of Michigan Institute for Social Research (ISR). “Multiple partner fertility is an important part of contemporary American family life, and a key component to the net of disadvantage that many poor and uneducated women face every day.”

For the study, Dorius analyzed data on nearly 4,000 U.S. women who were interviewed more than 20 times over period of 27 years, as part of the National Longitudinal Survey of Youth.

She found that having children by different fathers 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 multiple partner fertility. Women who were not living with a man when they gave birth and those with low income and less education were also more likely to have children by different men.

But she also found that multiple partner fertility is surprisingly common at all levels of income and education and is frequently tied to marriage and divorce rather than just single parenthood.

“I was a year into this project before I realized that my mother was one of these women,” says Dorius. “We tend to think of women with multiple partner fertility as being only poor single women with little education and money, but in fact at some point, most were married, and working, and going to school, and ...