Taj A. Isaiah admitted he had pretended at different times to be the husband, boyfriend or landlord of Roxanne Janel Jones, 35, of Kansas City, The Kansas City (Mo.) Star reported.
The scam victimized more than a dozen couples from throughout the country, the Star said.
Jones, 29, is accused of pretending she was pregnant and persuading prospective adoptive parents to give her money and food, among other things.
Isaiah, who an indictment said participated in the scam from June 2009 to March 201, pleaded guilty to one count of conspiracy.
Sentencing guidelines call for up to nearly 5 years in prison without parole.
The federal government dropped four counts of wire fraud against Isaiah as part of a plea agreement.
Barry R. Grissom, U.S. attorney for the District of Kansas, said the government is discussing a plea with Jones, who is in federal custody, but it had not been finalized.
Isaiah is free on bond until sentencing.
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