Anti-abortion groups are seeking a foothold on a new battlefield: custody disputes over frozen embryos.

Take the case of Jalesia McQueen and Justin Gadberry, a divorced Missouri couple in a court fight over the frozen embryos left over after the birth of their twins through in vitro fertilization.

The groups were recruited by McQueen’s lawyer for help in appealing a ruling that she could not use the embryos without the consent of her former husband. “This is the thing that kills me — having to fight to get my own children,” she said.

Gadberry wants no more children with her, and his lawyer, Tim Schlesinger, said his client resented the involvement of outside groups.

“My client views this as a private matter, between him and his former wife,” Schlesinger said. “They had an acrimonious divorce, and he doesn’t want another child with her. He doesn’t want his other children involved in a media circus. And he doesn’t want pro-life groups meddling in his private affairs.” Gadberry declined to be interviewed.

As scientific advances have made frozen embryos common, they have brought new complications to divorces. Most courts have treated embryos as marital property, often favoring the party that plans not to use the embryos, emphasizing a right not to be forced to procreate. Some have applied contract law, decided which half of the couple more deserved the embryos, or required mutual consent.

But anti-abortion groups argue that such cases should be decided according to the best interests of the embryos, the same legal standard used in child-custody disputes. In a friend-of-the-court brief filed last month in the Missouri dispute, they say an embryo’s most fundamental interest is to be born: “No other right is of any avail if a human being is not around to invoke it.”

Thomas Olp, of the Thomas More Society, a conservative public-interest law firm that filed the brief in concert with Missouri Right to Life and other anti-abortion groups, said: “Husbands and wives can divide up their property however they want, but embryos are living beings, so the legal standard has to be what’s in their best interest.”

His firm has also intervened in a much-publicized California case on the frozen embryos the actress Sofía Vergara made with her ex-fiancé, Nick Loeb, who wants to use them with a surrogate. Vergara’s request to dismiss the case was denied, but no trial date has been set.

Olp said his firm is likely to also join any appeal of recent cases in Chicago and San Francisco, involving women who froze embryos when they received cancer diagnoses and sought to use them after treatment, over the fathers’ objections.

The cases are part of the broader “personhood” debate that has become central to abortion politics. Advocates in many states are seeking laws that would make embryos full legal persons at fertilization — blocking not only abortion but also some forms of contraception and assisted reproduction. None have passed, and some anti-abortion groups say such laws go too far. But some Republican presidential candidates — Sens. Ted Cruz, Rand Paul and Mike Huckabee — support the personhood approach.

Anti-abortion groups turned their attention to custody of frozen embryos only recently. “Traditionally, even though excess embryos were produced, in vitro fertilization was seen as helping people have babies, so there was little interaction between that and anti-abortion advocacy,” said Lisa Ikemoto, a professor at the University of California, Davis, School of Law. “But as the debate over human embryonic stem-cell research heated up, anti-abortion groups woke up to the frozen embryo issue.”

Over the last decade, advocates seeking to represent embryos that might be killed in stem-cell research have challenged funding for such research, according to Judith F. Daar, a professor at Whittier Law School, but the courts rejected the cases, saying they had no standing to sue on behalf of such an amorphous group of embryos.

“These new cases are different in that they deal with specific identifiable embryos,” she said. “And the outside groups here are not trying to represent the embryos, but rather to make a case that the standard used should be the best interest of the embryo.”

The embryo disputes somewhat echo well-known right-to-die cases in which anti-abortion groups fought the removal of life support from patients in vegetative states — among them Karen Ann Quinlan, Terri Schiavo and Nancy Cruzan.

“The frozen-embryo cases make the same argument,” said Gerard Nieters, legislative director of Missouri Right to Life. “It’s an obvious area for us, since this is what we’re about, the protection of innocent human life, from conception till natural death.”

Also like the so-called right-to-die suits, the embryo cases raise questions about outside interest groups’ involvement in wrenching family disputes, like the one in Missouri.

In April, a Family Court commissioner found that the embryos were not children under Missouri law, but a unique form of marital property, which she awarded jointly to Gadberry and McQueen, for use only if both agreed. The commissioner, Victoria McKee, said using the embryos could violate the right not to be forced to procreate and create complex emotional tangles for the children.

“They would have to navigate why one parent did not want to actively parent the new child,” McKee wrote. “How difficult would it be for one parent to pick up the twins and not take an active role in the life of a new child standing right beside them? How difficult would it be for the newborn child?”

McQueen said she had told her 8-year-old twins that she was fighting for their brothers and sisters. “I answer their questions as best I can,” said McQueen, a lawyer who has formed an organization called Embryo Defense to support others in cases like hers. “It’s a very emotional thing,” she said.

McQueen added in an interview that she had for years considered herself a backer of abortion rights. But she is now very comfortable with her support from Missouri Right to Life, Lawyers for Life and the American Association of Pro-life Obstetricians and Gynecologists. “I would have been happy if the pro-choice groups had filed on my behalf,” she added, “because it is an important case and there are arguments on both sides.”

At trial, no one mentioned a provision in Missouri’s 1988 abortion law, which says that human life begins at conception and that “unborn children have protectable interests in life, health and well-being.” In the decision, McKee wrote instead, “Missouri courts and legislature provide no guidance on these issues.”

But the anti-abortion groups say failure to consider the Missouri law, plus the lack of scientific testimony on fetal growth, provides grounds for a reversal.

“This court should recognize, as the trial court did not, what science now unmistakenly establishes and what the Missouri General Assembly has acknowledged in the law of this state — new human life is created at the instant of sperm-oocyte binding,” their appeal brief said.

Schlesinger disagrees.

“The language is from the preface to an abortion bill,” he said. “No one was thinking about frozen embryos when it passed. And if anyone tried to enforce it, I would say it’s illegal under Roe v. Wade.”

Missouri has spawned other cases about the boundaries of personhood, including the Cruzan case, in which the Supreme Court established the right to die but found that the state could require “clear and convincing evidence” that the patient would have wanted that.

Missouri also produced the court’s infamous 1857 Dred Scott case, in which it ruled that a slave was not a citizen, but property — a parallel that McQueen’s backers draw. In their brief they wrote, “our sorry legacy of having enslaved human beings” should “raise a red flag of caution” about treating embryos as property.

© 2016 The New York Times Company