Stephanie Nelson was married for four months. The fight over the embryos she and her ex-husband created lasted for years.

Nelson was still married in 2020 when the fertility clinic called her at work with devastating news: Her husband had just requested the destruction of the embryos they created through in vitro fertilization, or IVF. During a fight the night before, he had said he no longer wanted to be a father.

She hadn’t thought he was serious until the call from the clinic. Nelson said she filed for divorce soon after.

Stephanie Nelson had to fight her ex-husband in court to keep the embryos they created.
Photography by Brittany Greeson for WSJ

That phone call launched a $10,000 legal battle for the now 37-year-old metal factory worker, who had saved for years to pay for IVF treatment. The case highlights what lawyers say has become a growing problem in divorce proceedings: What happens to frozen embryos when marriages end?

The answer can determine the fate of what is often a costly and emotionally taxing effort to have children.

President Trump last month announced a plan to make IVF cheaper , with costs remaining a major barrier to fertility treatment. A single IVF cycle including drugs can run more than $25,000, and many pay much of the cost out of pocket since most states don’t require insurers to cover it. But unlike a retirement account that can be divided or a house that can be sold in a divorce, embryos represent both the potential for life and lifelong financial obligations.

Nelson had known since age 23, after diagnoses of endometriosis and polycystic ovarian syndrome, that IVF was her only path to biological children. Over the years, she managed to put aside $20,000 for treatments.

She met her now ex-husband online in 2019. While dating, she told him about her infertility and the money she’d saved for IVF. She started treatments soon after, and they married roughly six months later. She said he visited a clinic in Georgia to provide sperm in March 2020.

“Head over heels, we just kind of did it without thinking,” she said.

More than one million embryos now sit in U.S. storage facilities, up from roughly 400,000 in 2002, according to the American Society for Reproductive Medicine. As IVF has expanded and success rates have improved, more couples are creating—and later fighting over—stored embryos, said Nidhi Desai, a Chicago fertility and family lawyer. “There are more embryos at play now.”

There’s no federal law governing the fate of embryos in divorce, and states vary in how they approach the matter. Courts across the country struggle with whether one person’s right to procreate outweighs another’s right to not become a parent against their will.

“Right now we have no idea, is an embryo property or is it a person?” said Nicky Rooz, a New York divorce attorney. “Is it custody you’re fighting over or what?”

Alabama’s high court last year declared frozen embryos “children.” Arizona law awards them to the spouse who intends to use them for birth, or the one most likely to do so if both parties wish to use them to have babies. Elsewhere, states may weigh factors like who underwent physical procedures, whether it is someone’s last chance at biological parenthood, and who paid.

Citing murky laws and growing case law, online service HelloPrenup last year added optional clauses to its forms to help couples spell out what happens to embryos in a breakup.

Nelson’s clinic contract didn’t address the matter, leaving it to courts.

“Please do not destroy my life’s work,” Nelson recalls saying in court. “This is my complete future. This is all I’ve dreamt about.”

Her ex-husband argued he had a right not to procreate, according to court filings. He didn’t respond to requests for comment.

A Georgia trial judge awarded the embryos to Nelson in 2022 after weighing her testimony that she couldn’t conceive without IVF, had paid for the treatments and had undergone the physical burden of egg retrieval, according to court records. The ruling was upheld in October 2024 by a Georgia appeals court.

Nelson said she paid $5,000 for her divorce attorney, then another $5,000 for a lawyer in the appeals case after her ex-husband challenged the initial ruling.

In other cases, agreements ahead of time can avoid protracted legal fights.

When Kate St. John, 31, started IVF in 2023, she got her husband to sign away rights to their embryos. “I think my intuition was like, hey, girl, you need to protect your reproductive options,” she said. The agreement stipulated that he would have no parental or financial obligations to any children she might have in the event of divorce. She used one embryo in 2024, which led to the birth of their daughter.

When their marriage ended this year, she kept the remaining embryos without a court fight.

St. John, who now lives in Fayetteville, Ark., pays $900 annually to store them at a Texas clinic near where she previously lived. Despite their agreement, she worries her ex-husband might rethink how involved he wants to be if more children result.

St. John’s ex declined to comment.

“Even if an ex-spouse agrees to no involvement, they could later seek visitation or custody once a child is born,” said Naomi Cahn, a family law professor at the University of Virginia who specializes in reproductive disputes.

Former spouses who no longer want to be parents could also find themselves obligated to pay child support, Cahn said.

In Michigan, Nelson is now pregnant with twins, using the embryos she fought for years to keep. Her new partner intends to adopt the twins. They’re considering a third child, using the remaining embryos.

Write to Dalvin Brown at dalvin.brown@wsj.com