US fertility clinic worker may have replaced customer's sperm with own

The University of Utah is investigating a complaint that a convicted felon working at a fertility clinic replaced a customer's sperm with his own, fathering at least one child, a girl, 21 years ago.

The mother of the girl, Pamela Branum, said she and her husband discovered a genetic mismatch in their daughter, and were able to trace her lineage with help from relatives of the now-deceased fertility clinic worker, Thomas Ray Lippert.

"I don't think we're the only ones," Branum told a television station in Salt Lake City, capital of the US state of Utah. "We think we're one of many" victims who used a clinic that was operated by faculty members.

The University of Utah said there was "credible" evidence of semen tampering or mislabelling. On Friday, the university said it was opening a hotline and offering paternity testing to anyone who used the clinic between 1988 and 1993. In a statement that stopped short of taking responsibility or naming Lippert, the University of Utah Health Care system said it appeared Branum's daughter was fathered by a clinic employee.

"It was hard at first, to think, 'Who am I?'" the daughter told the television station in San Antonio, Texas, where the family moved in 2003. "I thought I was this person [of] my mum and my dad. Now, my dad is not my biological father. Who am I?"