A U.S. woman has discovered that the sperm from a donor used to conceive her son seven years ago has been used to father as many as 150 children, raising concerns over the lack of regulation in the U.S. sperm donor industry.

Cynthia Daily, 48, a Washington social worker, has been tracking the number of children fathered by the same donor who also fathered her son on a website called donorsiblingregistry.com, according to the New York Times.

As artificial insemination becomes a more common practice for infertile couples or women who wish to raise a child on their own, Daily’s circumstance has increased concerns among parents, donors and medical experts about potential negative consequences of having so many children fathered by one donor.

Among them is the possibility that genes for rare diseases could be spread more widely throughout the population or that accidental incest may occur between half-sisters and half-brothers who live close to one another.

Each donor is identified by a specific number and for many parents who went through fertility treatments such as artificial insemination, that number is part of the basic "sexual education" in the family, according to the report.

“My daughter knows her donor’s number for this very reason...She’s been in school with numerous kids who were born through donors. She’s had crushes on boys who are donor children. It’s become part of sex education,” said an anonymous mother of a teenager conceived via sperm donation in California, the Times reported.

However, allowing too many children to be conceived with sperm from popular donors translates into huge profits for fertility clinics, according to critics.

That’s the same reason why many parents are asking for tighter regulations in the number of children that can be fathered by a same donor.

In the United States there are currently no limits to the number of children that can be engendered by a same donor.

The American Society for Reproductive Medicine recommends that no more than 25 children should be engendered from an individual donor per population of 800,000.

In the United States there are no official records of the number of children born through sperm donors as parents are not obligated to report the successful birth of a child through the process.

The U.S. Centers for Disease Control and Prevention has records of children born in the country through Assisted Reproductive Technology but those records do not include fertility treatments such as artificial insemination.

European countries such as Britain, France and Sweden limit the number of children fathered by a same sperm donor.