Two millenniums ago, in the foothills of ancient Greece, the physician and philosopher Hippocrates described pregnancy in terms of bread-making. In the thousands of years since, “a bun in the oven” has emerged as a euphemistic image for childbearing. That is, until a study suggested, in 2019, that pregnancy more closely resembles completing an ultramarathon.

This newer metaphor has taken hold on social media, where the hashtags #preconception and #pregnancyprep exhibit women treating pregnancy like “the biggest race of your life, except you don’t know when the race actually starts.” As any serious competitor would, these contenders prepare for months or even years before their gestational events by optimizing their physical conditions and mental health. “Here’s how I’m prepping to get pregnant this year,” one woman says, poised with an iPad in one hand and an Apple Pencil in the other. The caption reveals a sprawling list: “cycle tracking,” “strengthening the pelvic floor, deep core and glutes,” “balanced meals,” “daily meditations” and “financial prep.” It also offers a discount code for her chosen brand of fertility supplements.

This preparatory stage is sometimes called Trimester Zero, riffing off a 2017 book by the sociologist Miranda Waggoner that examines how public health initiatives affect reproductive risk. On social media, however, the concept has evolved into a set of pregnancy “solutions” offered by influencers and online health gurus to the “trying to conceive” (T.T.C.) demographic. The “elite pregnancy prep expert” (and systems engineer) Alexandra Radway, for example, promises that her Baby Ready Body method — a comprehensive “nourish to flourish” plan — supports “engineering healthy, fit pregnancies.” “You wouldn’t summit Kilimanjaro in flip-flops,” she writes in one post. “Pregnancy deserves the same respect.” With the right course of action, the trend implies, you can ward off all undesirable outcomes — not just morning sickness and exhaustion but, as Radway has suggested, even breast cancer.

That kind of mind-set seems to appeal, in particular, to prospective parents feeling trepidation. “I just want to start off by saying that I’m fricking terrified,” Kaylie Stewart shares, in one of seven parts of her ongoing “Prepping for Pregnancy” series. Another post begins with a similar declaration of terror but breaks into a calming montage: a slow walk down a leafy path, a home-cooked breakfast and makeup applied in a fuzzy robe, all set to a mellow tune. The video itself follows a remedial arc, as if its initial anxiety were transmuted, by the structure provided by preparation, into calmer, more productive energy.

Stewart’s content might be soothing to viewers who share her concerns. But TikTok’s For You page can inundate prospective mothers with plenty of other supposed threats. On the podcast “Culture Apothecary,” for example — which pursues “raw, unpasteurized truths” — the conservative influencer Alex Clark parrots unsupported risks of fetal exposure to Tylenol; her “Ultimate Guide to Pre-Conception” identifies dangers like mold, nail polish and food ordered from DoorDash. A large subset of preconception content also zeros in on “nontoxic swaps” for cookware, cleaning supplies, clothing, makeup and air filtration; even the right brand of organic cotton underwear is important, one influencer suggests, “if we want to see our future grandbabies.” (According to this thinking, your fate was decided decades ago by the brand of your grandmother’s knickers.)

In case that pressure wasn’t enough, “prepregnancy glow-up” posts promote plans for becoming not only the healthiest but also the hottest version of yourself before giving birth. “Welcome to a new era,” Gabrielle Meloff announces, by way of transitioning her profile from bridal content to “How I’m Getting Hotter & Healthier Before Pregnancy,” a preconception playlist that complements mood boards envisioning “planning for a pregnancy like a wedding” (featuring images like San Pellegrino in wicker baskets and early 2000s Christy Turlington practicing yoga and towers of rolled-up towels, presumably made from organic cotton).

These fantasies have arisen in a distinctly pronatalist moment, as many continue to push for higher birth rates. Yet material support for having children remains scant. Perhaps women online are simply reading between the lines: It’s on them, and them alone, to create conditions conducive for children. The content that encourages men to partake in prenatal prepping seems only to reinforce that women are exclusively responsible: Husbands aren’t prepping themselves, per se, but being prepped by their wives — who are now tasked with replacing their briefs with boxers and serving up meticulously researched, “fertility boosting” meals from scratch every day, having been permanently scared away from takeout.

After all, a woman online is most celebrated when she treats herself as a never-ending project. Preconception content, then, seems less like practical advice and more like a narrative starting point that allows the story of your life to perform well on social media. Motherhood can be described as tedious, uncertain or isolating — or as the new, empowering chapter for a person devoted to optimization. As one post — a slide show with Hermès baby blankets, bubble baths and freshly cut bouquets — reminds viewers, preparation for motherhood is also preparation “for life.” Its caption could describe any number of contemporary journeys, especially those that live on the internet: “What looks extreme to others is usually just preparation for the future they can’t see yet.”

Kim Hew-Low is an Australian writer living in Brooklyn.

For about a decade, scientists have had remarkable success curing some blood cancers by modifying a patient’s own immune cells to recognize and kill the malignant cells.

That same approach may help control H.I.V., among the wiliest of viruses, scientists will report on Tuesday. After a single infusion of immune cells engineered to recognize the virus, two people in a new study have suppressed their H.I.V. to undetectable levels, one of them for nearly two years.

The data is scheduled to be presented at a gene therapy conference in Boston, but the researchers shared an early copy with The New York Times.

The treatment is years, if not decades, from being widely available, but the study offers what scientists call “proof of concept,” and the tantalizing hope that a single shot could one day offer lifelong relief from H.I.V.

“It is inspiration and a potential road map to get to where we need to go,” said Dr. Steve Deeks, an H.I.V. expert at the University of California, San Francisco, who led the trial.

Other scientists were enthusiastic about the milestone.

“It’s truly amazing that they were able to accomplish this,” said Dr. Hans-Peter Kiem, an oncologist and gene therapy expert at the Fred Hutchinson Cancer Center in Seattle, who was not involved in the study.

H.I.V. requires lifelong control because the virus hides out in deep recesses of the body, and comes roaring back when it sees an opportunity. It also mutates easily to evade its attackers.

More than 40 million people are living with H.I.V. worldwide. About three-fourths of them take daily oral pills to keep the virus in check, and a much smaller proportion now receive injections every month or two. Several companies are developing longer-acting options, including weekly and monthly pills, and shots that could be given just once a year.

But scientists still aspire to develop “functional cures” that would effectively control H.I.V. over a lifetime, even if they do not eliminate it.

“People are really working hard on trying to cure it, and we’re making progress,” said James Riley, an immunologist at the University of Pennsylvania who is also modifying immune cells to control H.I.V.

Since the 1990s, many scientists have tried to modify immune cells called T cells to attack H.I.V., but those efforts were mostly unsuccessful. Some research teams lost interest after the arrival of powerful antiretroviral drugs soon after.

Cancer researchers soldiered on and succeeded in using the approach against blood cancers like leukemia.

“Cancer will always probably be the pioneer in this stuff, because of the incredible unmet medical need,” Dr. Riley said.

In the new study, scientists at Caring Cross, a nonprofit focused on developing affordable immunotherapies, engineered immune cells from each study participant to carry two molecules on the cell surface. Both molecules bind to H.I.V. and kill infected cells, but one also prevents the immune cells from becoming infected.

“It’s this dual nature of targeting — killing and protecting — that we think is the missing piece in terms of how this therapy works,” said Boro Dropulić, the executive director of Caring Cross, who developed the method.

The researchers extracted immune cells from each participant, modified the cells, then injected them back in. The participants stopped taking antiretroviral drugs the day of the infusion.

If a person does not take antiretroviral drugs, their H.I.V. levels typically soar within two weeks. But one person in the trial partially suppressed the virus for 12 weeks before rebounding. Two others were still in remission, 92 and 48 weeks after their infusion.

All three had begun receiving antiretroviral therapy within months of being infected. Three others who had lived with H.I.V. for longer before they were treated did not respond and needed to resume antiretroviral therapy. (A seventh participant showed signs of control seven weeks after infusion.)

Those details may be important. Those who were treated early in infection may have less H.I.V. sequestered in their body. Their immune system may also be less ravaged by the virus, and therefore more likely to rally when infused with the modified cells.

“Three out of three people with early disease doing some degree of control, to me, is the most provocative finding here,” Dr. Deeks said.

The two people with long-term response did show some blips of viral replication that quickly died down. That is to be expected as H.I.V. emerges from its reservoirs and is quashed by the immune cells.

Still, the results were exciting, several experts said.

The numbers in the study are very small but “these n-of-ones are so powerful because they encourage further research,” said Dr. Mike McCune, the head of a division at the Gates Foundation that supports innovation in H.I.V.

“For us, what’s important is to make sure that we can go from an n-of-one to an n-of-a-million or more,” he said. “And the only way to do that is to engage companies that know how to make products.”

The foundation has not invested in work that involves removing immune cells and reinfusing them back into the individual. That approach is too invasive and expensive to reach the millions who will need it, Dr. McCune said. But it is actively pursuing scalable options.

Cancer researchers are already showing success altering the immune cells while they are still in the body, which should eventually be cheaper by orders of magnitude.

The direct injections could be produced “for less than $10,000 and then be off-the-shelf, meaning you can have them ready when a patient or person living with H.I.V. comes in,” Dr. Kiem said.

Other groups are working on broadly neutralizing antibodies, rare molecules that can disable a wide range of H.I.V. versions by targeting parts of the virus that do not mutate.

“If we can combine these two approaches, that really may be synergistic and provide a pathway to deliver something close to a functional cure long term,” Dr. Riley said.

Anticipating long-term needs, Caring Cross is working with organizations in Brazil, India and elsewhere to manufacture the products for cancer at much lower costs. The team is also refining the tools and approach for H.I.V. and plans to begin a bigger study later this year.

“This is a first-in-human approach,” Dr. Deeks said. “We often come up with new theories as we do this, and that’s what’s happening as we speak.”