Sadie Holmes is more than 39 weeks pregnant and going into labor. She is sitting naked on the bed in the deluxe RV she calls home waiting for her next contraction to hit. While she waits, the 27-year-old brunette is filming a video for a fan. She wraps a measuring tape around her breasts, belly, and butt, while reading out measurements — 37 inches, 38 inches, 40 inches. “Mmm, look at that belly, and look at how swollen I am now,” she says, touching her pubic bone.

Then, a few seconds later, a contraction hits. “Ahhh, owww,” she says intensely, flapping her hands and sucking in air. She ends the video holding her belly and flirtatiously telling the camera, “I’m off to the doctor in the next few hours.”

In other custom videos ordered by fans, Holmes has done everything from stripping while gyrating her stomach to gorging on chips, burping uncontrollably, and complaining about being a “fat pregnant cow.” While pregnant, she’s also starred in professionally produced adult films featuring things like X-rated OBGYN appointments and faux incest — including one movie titled, “Daddy Made Me A Mommy Too.” Holmes, who has already performed during two pregnancies and plans to keep going, has found a foothold in the surprisingly popular genre of pregnancy porn.

It’s not the “pregnancy porn” that you see in grocery checkout lines, where tabloids endlessly speculate about Hollywood baby bumps and glossy magazines feature a rotating cast of pregnant celebrities doing the Demi and posing nude — but, really, it reflects all of the same conflicted cultural attitudes around pregnancy that are seen in the mainstream. Only it does so in the extreme, eyeball-grabbing terms of hardcore porn. It is all of our anxieties, hangups, and horror, as well as awe, intrigue, and reverence, around maternity writ large. Pregnancy porn is a magnifying glass, a revealing Rorschach test, for how we think of pregnancy itself — and, sometimes, a direct and compelling challenge to it.

Pregnancy porn is, without a doubt, a niche genre. It’s rare to find it as a featured category on tube sites or on offer from mainstream producers. Occasionally, it’s created by progressive female directors and queer porn producers — but it’s most often sold by fringe companies specializing in taboos, like incest, which tells you something about its standing in the adult industry. Still, pregnancy porn has a serious following. On Pornhub, it’s the 107th most popular search term in the U.S., alongside “redhead” and “babysitter.” It is much more popular, though, in the world of amateur porn and camming. On the X-rated cam and clip site ManyVids, “pregnant” is, remarkably, the number two most searched term, surpassed only by “anal.” In fact, users on the pregnancy fetish message board Preggophilia keep track of cam performers who are currently pregnant.

Last summer, 31-year-old Scarlett Lacy had been working as a cam performer when she found out that she was unexpectedly pregnant. “I was like, ‘Oh my god, there’s no way I’m going to be able to pay my bills,” she said. But then she started digging around the two sites she used, Clips4Sale and ManyVids, and found that pregnant performers were thriving. “It actually gave me hope,” she said. So, she started producing pregnancy clips that ran the gamut from what she calls “goddess fetish,” where it’s all about her being a “beautiful fertile woman” with an eroticized big round belly, to pretending to blackmail the viewer after tricking him into getting her pregnant to mocking a fan for not being able to get her pregnant. “It was insane and awesome — they did really well,” she said.

It seems fans don’t want any one thing from pregnancy porn. Holmes says many are titillated by the physical expansion that comes with pregnancy and enjoy tracking these details with OBGYN-like precision — one of Holmes’ fans paid for a series of updates throughout her pregnancy in which she would measure her expanding body parts and weigh herself. Some enjoy watching her pretend to be physically out of control while pregnant — say, gorging on junk food or groaning about the size of her belly. Another popular sub-genre is pregnancy cuckolding, where a man is belittled for failing to impregnate a pregnant woman. Sometimes there are shades of financial domination, where a pregnant woman orders a man that he must pay her child support, even though he didn’t father her child.

Queer and female-directed porn in this genre is less likely to treat pregnancy as taboo. Instead of titles like, “Pregnant & Pounded,” you get ones like, “Pregnant With Desire.” Storylines rarely focus on the pregnancy, which might not even be mentioned at all. “I wanted it to be nestled within the movie, that this would be a storyline that was happening within the movie but that we weren’t going to advertise on the cover,” said porn director Nica Noelle of her pregnancy shoots. “We weren’t going to make it a novelty thing.” In these kinds of films, pregnant bodies are eroticized, but it’s less about oiling up a woman’s belly than it is appreciating the full picture. Madison Young, a porn performer and director, and author of “The Ultimate Guide to Sex Through Pregnancy and Motherhood: Passionate Practical Advice for Moms,” starred in several films during her two pregnancies — mainly solo, queer, and lesbian scenes — and saw it as a way to “honor the complexity of our identity as human beings and to further honor the natural presence of sexual desire and sexual identity in all stages of our life.”

Sade Lune, who describes herself on Twitter as a “traveling bohemian courtesan, queerdo & parent,” is something of a pregnancy performance artist. She undertook a multi-part multimedia project titled, “Biological Clock,” about her desire to get pregnant — it included a short “art porn” film titled, “Egg,” featuring sex scenes interspersed with her inserting chicken and duck eggs into her vagina and then popping them out. The project culminated with what The Rumpus called a “queer insemination ritual/gangbang.” But Lune has also performed in what can be described more straightforwardly as porn and, once pregnant, she was excited to create films that showed “sexualized pregnancy that was not within the norm.” That meant performing as the dominant, and sometimes even sadistic, partner in several scenes — including one where she smacked her co-star around with her belly.

This might seem incoherent — that the genre presents pregnancy as taboo and grotesque but also natural and beautiful. That is partly because the adult industry is more diverse than people typically think, but also because porn tends to reflect back the culture that we live in — and, well, we are very conflicted about pregnancy.

Kelly Oliver, a philosophy professor at Vanderbilt University and author of, “Knock Me Up, Knock Me Down: Images of Pregnancy in Hollywood Films,” says attitudes around the pregnant body have done a complete 180, at least on the surface. In the 40s and 50s, it was something to be hidden. “Women were supposed to cover themselves up, stay at home, and were ashamed of being pregnant — I guess because it signaled that they’d had sex,” she says. In 1952, an episode of “I Love Lucy” dealt with the star’s pregnancy without once uttering the word “pregnant,” which was deemed too indecent to air.

By 1991 Demi Moore was posing fully nude on the cover of Vanity Fair while seven months pregnant — but the image was seen as so controversial it was sold wrapped in paper with only her eyes showing. Several decades later it feels de rigueur for pregnant celebrities to pose nude, whether it’s Jessica Simpson on the cover of Elle or Kim Kardashian in a naked selfie.

But it’s not so simple as to say that the pregnant body has been embraced. Tabloids celebrate Beyonce’s fertility goddess photo shoot or Serena Williams’ first-trimester Australian Open win at the same time that they critically obsess about celebrities’ excessive pregnancy weight gain or struggles to get back their pre-baby bodies. Mainstream film and television occasionally offer up soft-focus pregnant sex scenes, but maternity is often shown as comical and awkward, particularly when it comes to sex. “In a lot of these films the pregnant body is the butt of the joke, but it’s also highly eroticized, so you see a lot of it,” says Oliver. “It’s seen as sexy and attractive, but also kind of abject and yucky.” Then there are horror films, where women are pregnant with terrifying alien spawn — a not so subtle representation of reproductive angst, says Oliver.

“The pregnant body itself operates as a screen for those conflicted desires in our culture — desires around women, reproduction, motherhood,” Oliver said of mainstream film. It’s the same with porn, which delights in the pregnant body at the same time that it eroticizes our anxieties around it — whether it’s concerns about paternity, infertility, or female power. It shows pregnant women as both fertility goddesses and “fat pregnant cows” — and, every once in a while, just people.