By now, Mary Cheney must have inspired an entirely new chapter in "What to Expect When You're Expecting." Expect your pregnancy to provoke a national controversy.

It's been years since the vice president's openly gay daughter first created a stir on the right for her sexual preference and a stir on the left for her political preference. Now her "bump," as all celebrity pregnancies are described, is fodder for the sort of uncontrolled food fight she'll find all too familiar in another year or so.

Her opponents criticize her as a single mommy and one of two mommies. Her pregnancy has been labeled "unconscionable," "selfish" and "cruel." She and partner Heather Poe have been especially lambasted for bringing a child into the world "without a father." As Robert Knight of the Media Research Center moaned, "I think it's tragic that a child has been conceived with the express purpose of denying it a father."

It should be noted that 37 percent of all American children are now born to unmarried mothers. More to the point, Mary's baby does have a father, at least a genetic father. But have you noticed how little attention or criticism has been directed at the DNA dad?

There are, in essence, two kinds of fathers: known and unknown. The continuum of unknown fathers runs the gamut from the casualness of a one-night stand to the deliberateness of a sperm bank.

I am willing to guess that Mary and Heather chose a sperm bank as their matchmaker since these banks offer their customers — and I do mean customers — a screened set of genes from a diverse portfolio of men. The sperm donors range in height and ethnicity, athletic prowess and SAT scores. Some donors even provide an essay, sort of like a college admissions application.

It's fair to say that the sperm banks overtly promote the importance of the male gene in the creation of a child. And covertly promote the unimportance of the male presence in the raising of a child.

In the beginning, artificial insemination was a treatment for married couples with an infertile husband. Sperm donors, or sperm vendors as bioethicist George Annas calls the men who sell their genetic material, were often medical students who treated this as casually as a blood donation. The world and the child were expected to regard the husband as the biological father.

Today about 30,000 babies a year are born from sperm donors. The customers are now likely to be single women who have given up looking for Mr. Right in favor of Donor Right, and lesbians. But the donors are pretty much the same.

"Most of them are young guys trying to make some money and not thinking about the consequences," says David Plotz, author of "The Genius Factory," a book about a famous sperm bank. "They make a donation, it's kept in quarantine, released to someone they don't know and then a child is created with whom they have no connection."

This makes a perfect market solution: female customers who want children and male manufacturers ready to sell their genetic material without strings or custody suits attached. But sooner or later, the "consequences" grow up and may have a very different opinion.

One person's DNA is another person's "dad." Some children of sperm donors are beginning to search for their biological parents the way adopted children do. They're using information from sperm bank profiles, from DNA collection sites and donor sibling registries.

There is a growing belief that a child's right to know trumps the parents' right to keep a secret. Britain and the Netherlands have banned anonymous donors. In America, there are now two-tracked sperm banks — one for men who want to be anonymous, one for men willing to be contacted when the children become adults.

We can't ban sperm donation any more than we can ban the fertile one-night stand. We have no reason to keep single women, gay or straight, from the new technology. They can always go back to basics — or turkey basters.

But children, adopted or created, should have the right to find their biological parents at least when they grow up. It's time to end anonymity. If this gives men second thoughts about creating a child, well, we want men to have second — and third — thoughts. If it puts a damper on the genetic father market, who said that families were markets?

American society is in the midst of a great cultural change. Increasingly, we expect men to be involved fathers. We want fatherhood to be a commitment and not a donation. Let's stop the food fight over two mommies long enough to ask the question their child may ponder. Little Cheney-Poe: "Who's Your Daddy?"

Ellen Goodman is a columnist for The Boston Globe. Reach her at ellengoodman@globe.com.