When a couple conceived a baby via a sperm donor seven years ago, they ultimately hoped their son would one day get to know some of his half siblings. What they didn't count on is that there would be quite so many of them -- 150.   It was only when mom Cynthia Daily checked a Web-based registry for other children fathered by the same donor that she discovered how, er, prolific he'd been at sowing his seed.

“It’s wild when we see them all together — they all look alike,” said 48-year-old Ms. Daily, a social worker in the Washington area who sometimes vacations with her son's 'extended' family.

As more women choose to go it alone, and the number of children born via artificial means continues to rise, so too are the outsize groups of donor siblings.

But this begs the question: should donors be restricted to a sperm quota, say 10? After all, Ms Daily's donor is not the exception to the rule; many others donors are fathering up to 50 or more biological children.

Parents, donors and medical experts are concerned about the potential negative consequences of having so many related but estranged children, including the possibility that rare genetic diseases could be widely spread through the population.

There is even the risk of 'accidental incest' between half sisters and half brothers, who live in close proximity. Think about it. The concept is actually not as far-fetched as it may initially seem.

“They think their daughter may have a few siblings,” said Ms. Kramer who started a sperm registry in 2000, “but then they go on our site and find out their daughter actually has 18 brothers and sisters. They’re freaked out. I’m amazed that these groups keep growing and growing.”

Sperm donors, too, are (rightly) becoming concerned. “When I asked specifically how many children might result, I was told nobody knows for sure but that five would be a safe estimate,” said an anonymous Texan donor. “I was told that it would be very rare for a donor to have more than 10 children.”

He later discovered in the Donor Sibling Registry that some donors had dozens of children on file. “It was all about whatever [the sperm bank] could get away with. It is unfair and reprehensible to the donor families, donors and donor children.”

With fertility clinics and sperm banks increasingly interested in turning huge profits, they are ignoring the inherent irresponsibility of their actions. Shouldn't legal limits be placed on the number of children conceived by one donor's sperm? Does anonymity preclude ethics?

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