There are few things scarier than having a kid, as horror cinema knows all too well.

For decades, the genre has plumbed the depths of parental dread, from the satanic threats of Rosemary’s Baby and The Omen, to the monstrous birthing process (and subsequent nurturing responsibilities) of It’s Alive, to the more recent body horror terrors of Inside and the psychotic lunacy of The Babadook. In films of this ilk, the bun’s arrival in the oven is, for both men and women, a cause for not only joy but—as the unknown creature begins developing in ways that can’t be controlled, its arrival a surefire guarantee that the future will be very different (and likely more daunting) than the past—for mounting concern. Or, in the case of the latest nightmare to traverse this terrain, it may be reason to simply embark on a murder spree proposed, and encouraged, by the unborn fetus itself.

Prevenge is the right-to-death thriller that horror fans didn’t know they needed in their lives, a hilariously demented trip into maternal madness that, following its debut at the Sundance Film Festival earlier this year, will play this week at SXSW, and in select New York and L.A. theaters on the same day (March 24) it arrives exclusively on Shudder, the stellar AMC-owned horror movie streaming service. The brainchild of Alice Lowe, who wrote, directed, and stars, it’s a uniquely droll, gruesome saga that investigates the insanity that can arise from the anticipation of a baby’s birth. And in the process, it suggests something like a twisted joke about the abortion debate, recasting the issue of a baby’s welfare as one dictated not by external forces, but instead by internal impulses of a most deranged sort.

Opening with ominous, mysterious shots of a rocky cliff and the crashing waves below, Prevenge quickly picks up with Ruth (Lowe), a working-class British brunette sitting morosely on an outdoor swing, her protruding belly indicating that she’s not too far away from popping. Ruth’s far-off stare makes her appear more than a bit “off,” and that notion is wholly confirmed during her subsequent trip to a pet store. There, a creepy salesman (Dan Renton Skinner) laces his every comment about reptiles with deviant sexual innuendo (“That is my big fat snake”), to which Ruth responds with smiles and half-hearted retorts that barely mask her disgust. Thus, it’s a surprise when she agrees to join him in the back room to check out his more prized possessions—that is, until she reveals her true intent: to slice his throat from ear to ear, and then leave him lying in a pool of his own blood.

Cue some John Carpenter-esque synth music, and Prevenge is off on its malevolent way. After burning her clothes, Ruth writes crazy things in a notebook filled with scribblings about war, anger, fighting death, and “One Down.” She then checks into a hotel room, where her headboard begins to shake thanks to her neighbor’s violent shagging. Staring longingly at a photo of a man at the edge of a (familiar looking) cliff, she suddenly hears a voice emanating from deep within: “That’s how I was made. You can forget about that ever happening again. Selfish bastards. No consideration. We may as well not exist. Which is OK. I’m here.”

Ruth, it turns out, is in ongoing conversation with her unborn child. More troubling still, it appears that the midwife (Jo Hartley) whom Ruth routinely visits is right in opining, “You have absolutely no control over your mind or your body anymore. This one does. She’s got all the control now.” And as Prevenge soon makes clear, that forthcoming little one wants Ruth to kill, kill, kill.

Next on the docket turns out to be a clownish party entertainer named DJ Dan (Tom Davis) who she goes home with after a Halloween shindig. Putting up with his post-puke kissing in the back of a cab, as well as his bellowing at his elderly mom to stay in her room, Ruth eventually gets around to dispatching him in a way that speaks directly to her righteous fury at the sexual behavior that got her into this mess in the first place—and which will have most male viewers squirming in their seats.

The fact that Lowe was actually pregnant when she shot Prevenge certainly adds another perverse element to its slasher action, although it’s her performance—perfectly pitched between fury, regret, sorrow, and panic over how she’ll cope with her impending reality as a single mother—that truly helps root the alternately suspenseful, nasty, and hilarious material in genuine feelings of parental unease. Best known for her work in Ben Wheatley’s similarly-toned 2012 black comedy Sightseeers (which also married mirth with murder), Lowe has an open face that’s prone to going chillingly blank—or twisting into an open-mouthed lunatic snarl-grin à la the vengeful furies of her favorite movie, 1934’s Crime Without Passion. Pitiful and petrifying, she’s a lonely mommy-to-be with some less-than-stellar child-rearing instincts.

As it proceeds from one gory bit of business to another, Prevenge also equates its protagonist with other ne’er-do-wells of cinema history, be it A Clockwork Orange’s Alex (via a sequence set to Beethoven) and American Psycho’s Patrick Bateman (thanks to some office conference room bloodshed). Moreover, it ultimately reveals Ruth’s rampage to be driven by vengeance against those who committed a sin against her baby’s father. As such, it further turns the proceedings into a stew of twisted biological and parental anxieties and hang-ups, all of which are poised to tear Ruth apart, both figuratively and (get ready for some C-section slicing-and-dicing!) literally.

Whether indulging in cartoonishness like Ruth getting stuck in a tiny doggie door, or in gnarly mayhem (“It’s messy isn’t it: relationships, kids and responsibilities”), Lowe’s film crazily reimagines the abortion debate as one that’s out of both men and women’s hands; rather, it’s the prenatal tyke itself that’s both in charge, and has a fondness for bloody butchery. Begetting laughs as routinely as it does hands-covering-the-face scares, and thus earning its rightful place alongside its horror subgenre brethren, it’s a paranoid portrait of pregnancy as the harbinger of demented doom. Expectant mothers, take heed.