document: An American study of the prevalence of multiple partner fertility has found that 28 % of all US women with two or more children have children by more than one man . '' `` I was surprised at the prevalence , '' '' said demographer Cassandra Dorius , a postdoctoral fellow at the University of Michigan Institute for Social Research . '' `` 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 , '' '' he said .
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