Halfway through Rachel Lee Goldenberg’s road-trip comedy “Unpregnant,” the teenage protagonists swing by a carnival and climb aboard a whirling ride — not the most conventional spot for a heart-to-heart, but that doesn’t stop them. Gripping the ride’s restraints, Bailey Butler (Barbie Ferreira) and Veronica Clarke (Haley Lu Richardson) yell to each other and to the world around them. Bailey likes girls! Veronica is pregnant and going to get an abortion! They take turns yelling, “We’re gay and pregnant!”

“I had this realization at a certain point, when we were prepping: It works almost annoyingly well as a metaphor for the movie," Goldenberg, who directed and co-wrote the film, says of the scene. “They’re having this intimate conversation about important things, but we put them in this totally insane situation and leave them to deal with it there.”

Veronica’s unwanted pregnancy sparks the central journey of “Unpregnant,” the new HBO Max movie that begins with the strait-laced high-schooler asking her former best friend, the rebellious Bailey, to drive her hundreds of miles to a New Mexico abortion clinic that doesn’t require parental consent (unlike those in their home state of Missouri, where Veronica lives with her religious parents). Goldenberg never questions Veronica’s decision to get the procedure, a firm moral stance that allows her to approach the subject with humor.

With oddball characters and outlandish obstacles popping up along the way, the road trip winds up as zany as can be. Goldenberg cites both "Thelma & Louise” and “Mad Max: Fury Road” as inspiration.

This tone is where “Unpregnant” differs from most other films depicting the hurdles ahead of those seeking an abortion, including Eliza Hittman’s “Never Rarely Sometimes Always,” a poignant drama from earlier this year. Richardson, 25, recalls her initial surprise upon reading an early draft of the “Unpregnant” script, adding that she was nervous about striking the right balance of levity and gravitas. Ferreira says she was drawn to how the comedy worked to normalize a taboo topic.

“The same feelings that made me nervous about the movie and made it seem impossible . . . also excited me about it,” Richardson says. "I was like, ‘Oh, wow, this is going to be a challenge. But if we do it right, and it even kind of works, then it can start some real conversation.’”

Adapted from Ted Caplan and Jenni Hendrik’s novel, “Unpregnant” was an especially personal project for Goldenberg, 35, who notes that she got an abortion years ago and can relate to Veronica’s confidence and pragmatism toward the matter. Goldenberg didn’t tell too many people about getting the procedure at the time, an unconscious decision she attributes to cultural stigma. The sense of shame many are made to feel “has made room for more restrictive laws,” she says. The film’s messaging works against that.

At the same time, Goldenberg adds, “I’m a filmmaker, not an activist.” Her primary concern was to serve the story, and to mold the teenagers into well-rounded, nuanced characters. “Unpregnant” might surprise viewers by being more of a two-hander than its premise suggests; while it opens with Veronica’s predicament, Bailey’s emotional journey also rises to the forefront. They rekindle their friendship, whether by cathartically screaming at a carnival or evading the police who track down the car Bailey “borrowed” from her mother’s boyfriend.

Goldenberg offered the lead role to Richardson, whose dexterity as an actress has landed her diverse roles in teen dramedies like Kelly Fremon Craig’s “The Edge of Seventeen” as well as art-house pieces like Kogonada’s “Columbus.” She and Goldenberg worked together years ago on the set of a Lifetime movie about escaping polygamy and, upon reuniting for “Unpregnant,” developed a creative rapport that helped ensure Veronica didn’t become an uptight, popular kid stereotype.

“To be honest, I found Veronica pretty annoying at first,” Richardson admits. “But in the collaboration and trying to understand her, that’s when I started figuring out the things that I had empathy for her with. She feels like she needs to be perfect because of the pressure she puts on herself and society puts on her, and the expectations her friends and family have of her. She just does not want to let anyone down.”

Veronica and Bailey are positioned as opposites at the outset, the latter being more of a social outcast, though with a great deal of spunk. The two drifted as Bailey’s parents went through a divorce, a touchy history the film revisits when Bailey talks about her strained relationship with her father. Ferreira, 23, says she is drawn to projects that vary from her previous work. Though Bailey’s projected confidence recalls that of the actress’s character in HBO’s “Euphoria,” she broadcasts a different sort of complexity.

“I relate to her sarcastic, quick-witted humor and the way she deflects a lot of pain with humor,” Ferreira says. “I also relate to her having a different perspective on life. . . . Bailey sees outside of high school and sees outside of what everyone around her thinks, and forms her own opinions.”

The characters’s layers peel back as “Unpregnant” progresses, with Bailey showing moments of vulnerability and Veronica stepping up as the brave one every now and then. The actresses play off one another with ease, a dynamic they each say came to them naturally. They bonded over the difficulties of shooting in freezing temperatures in Albuquerque, goofing off between scenes to keep the frenzied road trip vibes going.

“For me, it was just really refreshing to see a movie that was made for young adults, that doesn’t dumb down anything . . . while also making sure that it shows a different perspective," Ferreira says. “It’s more of a story of two friends who are very different — polar opposites, pretty much — coming together and rekindling that connection and all that good stuff.”

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