Kathleen Whipple and her husband had dreamed of a big family, but struggled to conceive.

Upon his return from an overseas deployment with the Navy, the couple learned from a fertility doctor that her husband’s sperm count was half of what it had been before his most recent tour of duty, which had involved diving daily into water contaminated with heavy metals.

To get pregnant, the couple was told, they would need to undergo in vitro fertilization, a procedure that would cost over $25,000. And because they couldn’t prove that their infertility resulted from the circumstances of her husband’s deployment, they would have to shoulder the entire cost themselves.

“We would like to be able to purchase land and start building a home,” said Ms. Whipple, who is based in San Diego and asked to be referred to by her maiden name out of fear of retribution by the military against her husband. “We don’t have any savings anymore to do that.”

Such cases are the driving force behind an effort in Congress to expand military health coverage to cover I.V.F. for service members and their families, a push that has generated some degree of bipartisan support but has so far been thwarted by Republicans.

For months, advocates have hoped that this would be the year that the effort could succeed. President Donald Trump pledged on the campaign trail to make the procedure free for all Americans, then doubled down on the issue within weeks of taking office, issuing an executive order that promised to lower the cost of I.V.F. and expand access.

And Democrats won inclusion of the coverage expansion in the annual defense policy bill making its way through Congress. But the provision faces long odds after Speaker Mike Johnson intervened to kill a similar one last year.

Aides say Republicans are largely unconcerned with the public support Mr. Trump has expressed for the procedure, suggesting that the president may not be prioritizing I.V.F. policy to the extent he did during the campaign. The Trump administration has yet to announce any policy plans on in vitro fertilization, though a report on the subject was prepared for the president last spring.

A White House spokesman, Kush Desai, said the Trump administration would soon announce further plans on in vitro fertilization.

“The president remains committed to expanding I.V.F. access for Americans looking to start families,” Mr. Desai said.

Many Christian conservatives are deeply opposed to I.V.F., a procedure in which the egg is fertilized outside of a woman’s body, because the procedure can involve discarding human embryos. After staying largely silent on the matter in the wake of an Alabama Supreme Court ruling last year that restricted the procedure, a growing coalition is now rallying around a “natural” approach to infertility called restorative reproductive medicine — and working hard behind the scenes to steer the Trump administration away from I.V.F.

Republicans are “terrified of being put on the record because they know they’ll be attacked by the anti-choice people,” said Senator Tammy Duckworth, the Illinois Democrat who led the effort to include the proposal to cover I.V.F. in the Senate’s defense bill. “They don’t want to talk about it. They just want to avoid it.”

Representative Sara Jacobs, the California Democrat who led the House proposal, said she was “trying to work with the White House to have them help get this across the line.”

“We know they’re looking for ways to actually implement the E.O., and so we’re hoping they’ll take the win,” she added, referring to the president’s executive order on expanding I.V.F. access.

Both members of Congress have had fertility treatments themselves and said their personal experiences inspired them to write legislation to help service members afford the costly procedures.

The House passed its version of the defense policy bill last month, and eventually congressional leaders will have to reconcile it with the Senate’s version of the measure, which is still pending, in closed-door talks. Proponents are unsure whether the I.V.F. coverage provision will survive those final negotiations this time or suffer the same fate as last year, when it was pulled before the bill was sent to the president’s desk.

“While we have great sympathy for couples who are having difficulty starting a family, I.V.F. is ineffective, leads to the destruction of innocent human life, and does nothing to treat the root cause of a couple’s infertility,” Representative Josh Brecheen, Republican of Oklahoma, and Matthew Rosendale, a Republican representing Montana in Congress at the time, wrote last year to House and Senate leaders, urging them to remove I.V.F. expansion from the defense policy bill.

A senior Republican aide involved in private discussions on the issue, who insisted on anonymity to talk about them, noted that many Republicans are concerned about the high cost of expanding I.V.F. coverage for military members. He added that Republicans had discussed covering restorative reproductive medicine for service members instead, a less expensive approach that treats what proponents call the “root causes” of infertility.

Physicians who specialize in the approach analyze patients’ diet and exercise habits, while helping them chart their menstrual cycles, a process that can help expose certain reproductive health conditions. Practitioners treat reproductive health conditions but do not offer I.V.F., a posture that has prompted harsh criticism from leading medical associations. The American College of Obstetricians and Gynecologists has called restorative reproductive medicine “unproven” and “not a medical term.”

Connor Semelsberger, a government relations director at the conservative Heritage Foundation, argued that military members should be able to access restorative reproductive medicine as an alternative to I.V.F.

“When it comes to service members,” he said, “I think the most beautiful thing for a couple to be able to do to is find out what the health issues are that are causing their infertility and find a remedy for that.”

He added that the military had expanded infertility coverage significantly in recent years, offering I.V.F. for qualifying service-related injuries and illnesses, and covering the cost of travel if someone needs to access infertility care far from their home.

But Ms. Duckworth argued that expanding I.V.F. coverage is a retention issue for the military, since service members who reach their later childbearing years and realize they may need fertility treatments can be some of the “most highly trained individuals.”

“These are the folks who have probably 10 years of military experience,” she said. “This is like the backbone. So you’re going to lose the leadership of your military if they can’t get coverage, and so that does affect the lethality of our military.”

For guidance on how to navigate paying for in vitro fertilization in the military, many service members and spouses turn to support groups on Facebook, said Chandler, a military spouse who recently got pregnant through I.V.F. She spoke on the condition that only her first name be used, out of fear of retribution against her family and privacy concerns.

The logistics surrounding the procedure can vary from place to place, she added, with certain hospitals on base providing some I.V.F. services that others do not.

“People will share pictures of a breakdown of how much is covered at a particular clinic, or a breakdown of how Tricare may cover this or that,” she said, referring to the health insurance program for the military. In the support groups, she added, some people discuss how they tried to secure an overseas deployment to a country where I.V.F. would be less expensive.

Chandler said she was able to “pull a few strings” to secure care at a military clinic on base meant only for service members. There, she said, some of her infertility treatment was covered, though she still had to pay $10,000 to an off-site clinic that handled the egg retrieval and embryo transfer.

“I don’t know how I got so lucky,” she said. Reading through the posts on Facebook, Chandler said, she feels extremely frustrated that such coverage isn’t simply provided for all service members.

“We are asked to do so much — all the moving and everything, partners being away on deployment — and all those things that impact your ability to have a family,” she added.

For some military spouses, a part-time job is the best route for I.V.F. coverage when the government is unwilling to cover the procedure. One option is to turn to Starbucks, said Katy Bell Hendrickson, the wife of a retired Navy SEAL and co-founder of the Military Family Building Coalition.

“Become a barista and have a baby,” she said. The coffee megachain covers up to $25,000 in fertility care for employees who work 20 hours a week or more.

The Defense Health Agency, which runs Tricare, the health insurance program for the military, and the Navy both declined to comment, and the Pentagon said it would not comment on pending legislation.

Members of the military face higher rates of infertility than civilians.

A Defense Department-funded study conducted under the first Trump administration in 2020, at the request of Congress, found that half of active-duty servicewomen reported they had “delayed getting pregnant or starting a family” while in the military. Over 15 percent found it difficult to become pregnant when they began trying for a baby. The number climbed to almost 22 percent when looking at married active-duty servicewomen.

The study stressed the importance of making it easier for women in the military “to parent without putting off career advancement,” noting that I.V.F. is not currently covered for the majority of servicewomen, and that 43 percent would consider freezing their eggs if the procedure was “completely covered” by the military.

A separate congressional report said radiation and the physical demands of military service may contribute to infertility among service members.

Service members are also at risk of higher exposure levels to toxins than what “you’re seeing in the general population,” added Joseph Bressler, a toxicologist at Johns Hopkins University. He said that toxic exposure can impact female and male reproductive systems, including sperm count.

After several miscarriages and a failed embryo transfer, Ms. Whipple conceived her second child through I.V.F. in 2023.

“We used to always just say, ‘Well, we’ll be happy with whatever God gives,’ ” she said, her 1-year-old daughter cooing in her lap. But Ms. Whipple still holds out hope that she and her husband could try for one more baby before she is past her childbearing years.

They could only afford another I.V.F. transfer if the military covered the cost.

If Congress expands coverage, she said, “we still have three embryos.”