How many parents can a baby have?

Coming soon to a courtroom near you: five or more people all claiming to be the rightful parent of a single child.

In this era of advancing reproductive technologies, one baby may, indeed, result from an egg donor, a sperm donor, a woman who carries the baby during gestation, and the couple who intends to raise the child.

If that's not confusing enough, the biological father may be dead for years by the time the child is actually conceived, a situation made possible by stockpiles of frozen sperm.

The reproductive jumble is shattering traditional definitions of parenthood - and leaving courts all but begging lawmakers to settle the uncertainties surrounding newborns whose parents haven't been legally determined.

"Many more actors have become involved in the drama of reproduction, and courts are increasingly being called in to sort out their rights and responsibilities," says Lori Andrews, a professor at Chicago-Kent College of Law.

Just last week, Massachusetts' highest court held that children conceived using the frozen egg or sperm of a deceased parent could be considered offspring for the purpose of inheritance. The case was brought by Lauren Woodward who, using her husband's frozen sperm, conceived twins 16 months after he had passed on.

The same day the court heard the Woodward case, it considered arguments in another "who's the parent?" case. A couple was asking the court to put their names on the birth certificates of their newborn twins - rather than the name of the woman who gave birth to the babies after the couple's egg and sperm were implanted in her womb.

In both cases, the Massachusetts Supreme Judicial Court said it shouldn't be the one making these decisions. "The questions ... cry out for lengthy, careful examination outside the adversary process," Chief Justice Margaret Marshall wrote.

Conflicts over frozen reproductive materials and the resulting children will only get more complicated as technology advances further, says Arthur Caplan of the University of Pennsylvania's Center for Bioethics.

Already, more children are born each year in the US with the help of reproductive technologies than are put up for adoption. And disputes are proliferating as couples who created tens of thousands of frozen embryos decide to divorce - and vie for ownership of the embryos.

As a result, the traditional definition of motherhood - a woman who gives birth to a child - no longer fits all circumstances, lawyers say. The birth mother may be only a carrier for donated sperm or eggs - or, someday soon, even a transplanted ovary.

"Children are being born into a legal limbo that is putting them in legal jeopardy," says Connecticut state Rep. Patrick Flaherty.

The uncertainty frustrates parents such as Nancy Hart, who conceived a daughter in 1990 using her husband's frozen sperm three months after he died. "The truth was he was her father, but the law said she has no father," says Ms. Hart, whose fight through the courts to get Social Security benefits for her daughter led her to attend law school.

Hart and attorneys who represent other parents say biology can no longer determine parenthood when so many people may contribute genetic material to a single baby. Instead, the parties' intent, at the time the genetic material was donated or the baby was conceived, should govern, they argue.

Observers say states need laws that consider both couples' desire to reproduce and the resulting child's best interests. So far, though, few legislators seem willing to contend with those who oppose reproductive regulation, from abortion-rights activists to feminists to some churches.

As a result, the field of reproductive technology is largely unregulated. Though the first posthumously conceived child was born more than a decade ago, many issues surrounding rights of such children are still being sorted out.

A few states are starting to address these topics. Louisiana last year opted to give inheritance rights to posthumously conceived children, while Texas requires the consent of the husband before his death to use his sperm.

Connecticut considered legislation last year that would update the statute governing artificial insemination to include egg donations and the transfer of embryos. Under the bill, parents would be able to establish legal parenthood well before the birth of a child. The legislation didn't pass, but Mr. Flaherty, the bill's sponsor, plans to reintroduce it this year.

In the absence of state laws, courts are the ones forced to resolve disputes - and they are generally doing so in ways that revolve around the narrow circumstances of the case, Chief Justice Marshall of Massachusetts noted in last week's ruling.

Judges in these cases wind up validating decisions of doctors, patients, and entrepreneurs, says Elizabeth Bartholet, a family law professor at Harvard University. But no one, she warns, is asking basic questions such as whether allowing posthumously conceived children is desirable. "There are a lot of policy issues - the health of the egg seller, commercialization of reproduction, and whether kids should be brought into this world not knowing their parent - that aren't being addressed."

But as Judith, Nancy Hart's daughter, turns 10, Hart says neither has doubts about her decision. "She'd love to have a father, just like she wants a baby brother," says Hart, a lawyer in Beaumont, Texas. "But she's very well adjusted and very happy."