If you look up the ins-and-outs (no pun intended) for how pregnancy works, you’ll find the most clinical, harrowing, and unsettling description of a parasitic body horror story imaginable. Phrases like “constant access to the mothers’ blood supply for nourishment and growth” and “genetic melding” sound less like the magical, soft, awe-inspiring miracle of life that the experience is assumed by many to be, and more like the first pass at a film to be directed by John Carpenter or David Cronenberg. While it’s true that many pregnancies — particularly those by young, fertile, cisgendered, white women — go off without a hitch, and are often just the normal kind of horrifically beautiful experience, the act of pregnancy, both those wanted and planned or unwanted and surprising, are the very model of some of the best tropes and triggers for storytelling when it comes to body horror films.

For the sake of film, pregnancy is a marvelous trope to be harnessed; playing on not only a vision of innocence on behalf of both mother and unborn baby, but on the acute vulnerability and fragility that comes with people who are with child — not even mentioning the many allegories for infestation, pollution, or the crossing of lines between the body’s self and the self that can inhabit it. For all that the sight of an embryo can inspire, it also conjures up images of placentas, vascular membranes, blood, and the expulsion of a creature that, while entirely known by its host in almost all circumstances, is nonetheless an unknown creature never before seen in this world; a new unheard of life form brought onto this earth every 4.3 seconds.

“It sounds like you’re talking about an actual horror film”, said my partner upon reading those first two paragraphs. And really, they’re not far off, and that’s for a good reason. By definition, body horror is meant to be a fear that strikes us on a biological and evolutionary level; a threat to an otherwise ordinary way of existing in one’s body, whatever that ordinary may be for each individual viewer. A break from the norm that threatens to make us what we normally could never be, or worse, make us something better and more suitable for something else. Thus, the sub-genre of horror has built itself around the showcasing of intensely graphic — or psychologically disturbing — violations of the human body, ranging between the use of disease or parasitic infestation to morph the body, the lack of control over one’s own body, or a monstrous version of what the human the body can be made into through force. Luckily for horror junkies and filmmakers alike, pregnancy as a concept (and a reality) is the perfect vessel for which to tell these stories, because of the pregnant person’s lack of control over their own body given the choice or not.

Rosemary’s Baby continues to be a shining example of pregnancy used as an expertly crafty trope. While Rosemary Woodhouse believes she has the perfect husband, and the perfect new dream apartment, her life becomes a host to manipulations, tragedies, and physical exhaustion after falling pregnant — not by her husband Guy, but from the devil, conjured by their neighboring witch coven. There’s layers to why the body horror in Rosemary Baby works, not least of which because much of it involves little tangible horror at all; instead preying on Rosemary’s naivety and the excitement of a young expecting mother. From conception (a scene that is still one of those disturbing and unsettling in the genre’s long history), Rosemary’s pregnancy is dictated by those around her. What she drinks and eats, when she sleeps or doesn’t, what doctors she’s allowed to go to, what books she’s allowed to read — all kept to a strict boundary of what the coven (unbeknownst to Rosemary) knows is best for the growing anti-christ in her womb.

Even towards the end of the film when Rosemary gathers her strength enough to push back, she’s gaslit until near-hysterical; giving birth to the Antichrist and, even then, still tricked into believing that if she truly wanted to be a mother, she would love him and raise him as a mother anyway. Filmed close to the years of the Women’s Liberation Movements of the late 1960s, it’s clear that the control of women’s body was a hot button issue; but even fifty-three years later, the concept of a child-bearing persons’ body being under control of others is hardly a horror that has surpassed us. Your body is capable of hosting, and thus, you will be chosen whether you like it or not.

A similar theme pops up in the 2019 film Swallow — a movie that, while billed as a psychological thriller, is more than happy to blur the lines between psychological and physical (that is to say, body) horror found when pregnancy doesn’t go quite as planned. Hunter, a lower-class girl newly married to generationally wealthy husband Ritchie, no longer has to spend her time toiling away at a menial job; instead she gets to stay home and play the role of perfectly poised housewife in their upstate New York home. Despite the luxuriousness of her surroundings and marriage, Hunter is deeply unhappy and feels stifled and controlled by both the under-the-radar emotional manipulation of her husband, and the grasp of his parents with regards to the couple’s finances. Nonetheless, Hunter becomes pregnant and is more than grateful enough to put up the mask of happiness for the sake of a comfortable life for herself and her baby. She’s only able to keep up the charade of joy for so long, however, as she develops a severe case of pica — a disorder that compels its sufferers to eat inedible objects — after swallowing a marble following her pregnancy announcement, and finding relief and exhilaration after eating it.

Hunter’s compulsions become more and more intense as the audience is shown the quiet spiral of Hunter ingesting more marbles, buttons, and, eventually — upon finding out her husband and his family had been bribing her psychiatrist for information on her after months of severe judgement and smothering “help” for her disorder — a miniature screwdriver. Without spoiling the ending for those unfamiliar with this particularly unsettling film, Swallow does a marvelous job of not only presenting a variation on the gaslighting and infantilization-of-pregnant-women story as seen in Rosemary’s Baby, but adds an extra flare of physical horror as we watch Hunter stuff her emotions — and stifle her reality of pregnancy from a horrible man — with otherwise indigestible objects. While pica is something that many pregnant people suffer from, the severity in Hunter’s case, mixed with her psychological pain, is nothing if not a multi-level example of the ways that the human body — particularly a child-bearing one — can be anything busy, familiar or comforting.

Then there are, of course, the more extreme examples of fictional pregnancies that — for all that they could and arguably should be as beautiful as the many self-help books and common wisdom promise — are nothing short of horrific, simply because they lean into the idea of the mother birthing a monstrosity. Geena Davis’ experience in David Cronenberg’s 1986 remake of The Fly, or the genuinely disturbing classic The Brood (another Cronenberg movie; that director being no stranger to body horror as metaphor, as anyone familiar with Videodrome can attest to) are shining examples, showing more physical aspects of pregnancy and birth associated with bringing the unknown into the world. While these movies may feel like an uncomfortable and unyielding extreme when one thinks of their bouncing little bundle of joy, the very concept of “the unknown” remains a constant until the creature is forced into the world or forcefully removed from it. (And as someone who had recurring nightmares about Cronenberg’s “pupa baby” in The Fly during their entire pregnancy, I’d say the effect holds up pretty well.)

Some films obviously push this idea deeper into traditional monster territory in order to fit their genre: 1980s classic Aliens transformed the claustrophobic dread of the Ridley Scott original into a (in)famous metaphor for warring motherhood, with chest-bursters now getting featured on birthing cards for expecting parents as a result. Even John Carpenter’s The Thing — like Cronenberg’s The Fly, a remake and update of a B-movie from decades earlier — gets to gain some Pregnancy Horror traction from the idea of your body being consumed to make another living thing, forever changing how you’re able to interact with the world! Beyond the Door, Grace, mother!, Baby Blood — the list goes on. But one thing remains constant throughout all of these films and many others in the genre regardless of their specific take on birth and pregnancy, however: no matter the details, any viable — which is to say, fertile — person is, consistently, a potential host for the soon-to-be-revealed unknown.

In a time where child-bearing persons are often forced into gestational roles when they’re not prepared, or are given lesser care because of preconceived ideas regarding their specific pregnancies, there is no shortage of real life horror to be found surrounding the very notion of pregnancy itself. Beyond the political and social machinations of people seeking to control others’ bodies, there remains one simple, single truth: what many consider to be the all-consuming miracle of giving birth is, in fact, something that remains mysterious despite the depth of scientific inquiry and discovery on the topic — and, because of that mystery, indeed, because of what has been discovered in search of solving that mystery, the reality of pregnancy is the most common occurrence of actual body horror that exists in the world today.