Stephanie and Anthony are twins, 4 months old, and they split their time between two households. Their parents are fighting over them, but they aren't typical children of divorce and remarriage.

The custody battle, now under way in Michigan, is between Laurie Yates, a surrogate mother who recently gave birth to the twins, and Barry Huber, the Arkansas farmer who is their biological father.

Last week, Judge Timothy Green of Gratiot County Circuit Court found the surrogacy contract unenforceable. "I think it goes without saying that surrogacy denigrates human dignity," Green wrote. "Contracts of surrogacy are void as contrary to public policy."

Yates and Huber now face a traditional custody battle without reliance on the surrogacy contract. Yet the questions that surround new reproductive technologies are far from settled.

Some ethicists reject all new technologies for conception. The Vatican, in a statement issued last March, described all techniques that create life outside the body as "morally illicit." Nevertheless, more and more couples are turning to high-tech medicine to have children.

So far, about 600 children have been born to surrogate mothers, who were paid to be inseminated with a man's sperm and then, according to contract, hand the baby over to the father and his wife.

"Only about 1 percent or less of surrogate mothers change their minds," said Lori Andrews, a research fellow at the American Bar Foundation in Chicago. "We usually attribute it to something special about motherhood, but the fact is that among men who donated sperm for traditional artificial insemination, there are also some who later wanted access to the child."

Only a few such cases have gone all the way to court, Andrews says; usually, when the surrogate mother changes her mind, the biological father gives up his claim to the baby.

Last winter the highly publicized "Baby M" case, in which the father fought for and eventually won custody of his contracted-for child, forced legal and ethical experts to question surrogate motherhood contracts.

"A surrogate mother should be allowed to change her mind," said Matthew Myers, an attorney representing Surrogate Motherhood Inc., a Laurel group that pairs infertile couples with surrogate mothers. "But a surrogate motherhood program ought to be based on the presumption that she won't."

In ruling on Mary Beth Whitehead, a surrogate mother from New Jersey who changed her mind after giving birth to Baby M in March 1986, New Jersey Superior Court Judge Harvey Sorkow decided that the surrogacy agreement was a "valid and enforceable contract."

According to Sorkow, Whitehead had had the right to change her mind even after the contract was signed. But she lost that right at the moment of conception. Whitehead is appealing to the New Jersey Supreme Court.

"This is a very forward-looking court," said Andrews. "It's the court that made the {Karen Ann} Quinlan decision and heard other cases about termination of care and similar matters." She expects its decision to be a precedent for other surrogacy trials.

But Myers thinks it will be years before any precedent will be set in surrogacy cases. " A number of issues that are purely legal, that don't carry the moral or social stigma of this one, do rely on precedent, and the first important decision tends to have a major, major impact," he said. "But no judge, no jury comes to the issue of surrogate parenting without some strong personal biases. I believe that until several more decisions come out, each jurist will want to consider each case on its own."

Meanwhile, the technology of reproduction continues to advance. The newest twist on surrogate motherhood, called ovum transfer or surrogate gestational motherhood, further complicates the legal and ethical debate. In ovum transfer, a couple's egg and sperm are joined in the laboratory, and the embryo is implanted in a second woman's uterus. She carries the baby for nine months and gives birth to the child, but she has no genetic connection with the infant.

"There are those who think the gestational mother is just babysitting for nine months," said Susan Hicks, a Fairfax attorney representing a woman who gave birth in this way on Dec. 21. The woman Hicks represents, known in court papers as Jane Roe, bore a baby girl for her good friend, a married woman who had been born without a uterus. The baby was conceived by in vitro fertilization of the egg and sperm from this infertile couple, and the embryo was implanted into Roe's uterus.

Roe wants to have her friends' names rather than her own placed on the birth certificate as the child's mother and father. She asked for a ruling last August from the Fairfax Circuit Court, which has yet to decide on the matter, said Hicks. So for now the baby, named Virginia, is at home in Massachusetts with her genetic parents -- who were confirmed as such by a blood test taken when the baby was a few weeks old. Pending the court's decision, Virginia's birth certificate is still blank.

"The biological parents do not want to have to adopt their own child," said Hicks. And it's not even clear they could; in an ironic Catch-22 that results when technology outpaces the law, an adoption in Virginia requires that the petitioners receive consent for adoption from the baby's natural parents. In cases involving ovum transfer, the natural parents and the adoptive parents are the same.

If a surrogate mother in an ovum transfer case changes her mind, her claims to the baby would be less than those in a case like Mary Beth Whitehead's, experts say, because the woman has no genetic connection to the baby she carries. "But I think she's more than an oven with a muffin inside her," Hicks said.

According to Hicks, common law, which could not have predicted such complex reproductive arrangements as surrogate motherhood, considers a baby's mother to be the woman who gives birth to the child. "But ovum transfer introduces the prospect of a baby on whom two women both have, in effect, equal legal, moral and natural ties," Hicks said.

Only three other ovum transfer births have been recorded: a Michigan baby born in April 1986, a California baby born last spring, and South African triplets born in October 1987. Matthew Myers said his organization recently arranged an ovum transfer, and the surrogate gestational mother expects the child in late 1988.

The South African woman who bore the triplets last year, 48-year-old Pat Anthony, is being called "Surrogate Granny" by the tabloid newspapers. The babies she gave birth to were in fact her own grandchildren; they had been conceived through in-vitro fertilization of the eggs and sperm of her infertile daughter and son-in-law.

Legislation has been introduced in at least 27 states that would place some restrictions on surrogate motherhood. To date, only two laws are on the books: Arkansas provides that if a surrogate is unmarried, the father and his wife are the child's legal parents, and Nevada has an exemption in its babyselling laws that explicitly makes it legal for a surrogate mother to accept payment. (The going rate now is $10,000 plus medical expenses; arranging for a surrogate birth, including all legal and medical fees, usually costs a couple $20,000 to $25,000.)

Last year, D.C. Council member John Ray introduced a bill that would ban payment to surrogate mothers or sperm donors. "I think that would be misguided," the American Bar Foundation's Andrews said, because it would make surrogate relationships more exploitative, not less so.

As it is, she says, the fee a surrogate is paid works out to about $1.50 an hour, "compared to the $25 to $100 paid to a sperm donor for a few minutes' work."

Andrews sees nothing wrong with paying surrogates for their role in producing children. "In my opinion, child-rearing is a much more important part of parenting than child-bearing," she said, "and we're perfectly willing to pay babysitters and day care centers and nannies to stand in for the the parents in that role."