“Next time you pee, just notice what you’re doing with your face,” a doula tells Jackie (Jess Weixler) less than a minute into “Fully Realized Humans,” a seemingly impossible task when the expectant mother feels no control over her life at the moment, let alone her body. Her husband Elliott (Joshua Leonard) is having his own anxiety when the prospect of becoming a father is stirring up memories of his tortured memories of his own taciturn dad, and as Jackie explains to the doula, who just hopes to give her a better understanding of the physical changes she’s experiencing, she can’t even shop a Target without a “DEFCON 3 meltdown,” paralyzed with fear about the right car seat to get when the fact that the cheapest one also appears to be the most efficient gives her pause.

These nagging concerns sound eerily authentic, surely in part because Weixler was actually eight months pregnant when filming the third narrative feature from Leonard, whose first “The Lie” also paired him with the actress to play a couple wrestling with their new responsibilities as parents, only that was after their characters had the child. Nearly a decade later, the intervening years appear to have lent considerable wisdom to the de facto prequel, observing how Jackie and Elliott’s fixation on pregnancy-related minutiae has blinded them to accepting that some things just can’t be planned for. After a baby shower from hell where somehow the conversation changes from celebratory small talk to chatter about crib death potential and the perils of breast feeding, the two resolve to spend their last four weeks before the due date indulging in the wildest activities they can think of to excise their fears, with relatively innocent misdeeds such dine ’n’ dash quickly giving way to more extreme measures. (Needless to say, the real-life baby growing inside Weixler’s stomach won’t be seeing her mother’s work in this any time soon.)

Not every pair of real-life friends can translate their good times into one for the audience, but Weixler and Leonard are truly exceptional in this regard, clearly comfortable enough in each other’s company to take “Fully Realized Humans” to the crazier places it goes without ever seeming far-fetched in testing their bond and the relaxed chemistry just right for a pair that learns to loosen up. Like “The Lie,” which Leonard made in the wake of his breakthrough turn in Lynn Shelton’s largely improvised “Humpday,” the director leans on his actors to craft their own scenes, and while some run a little long, the dedication to finding authentic emotional moments is as appreciated as the many unexpected jolts of comedy along the way.

There are also clever aesthetic touches that remind of the skilled hands behind a production that feels completely casual, with Leonard luring back Benjamin Kasulke as a director of photography following his accomplished directorial debut “Banana Split” to reflect how Jackie and Elliott are pulled further and further off their axis with his savvy camerawork and securing a minimal yet inspired score from Luke Fabia and Peter Raeburn that repurposes instruments you’d find in a nursery for wonderfully creepy and catchy musical accompaniment. Although you can’t be sure at the end of “Fully Realized Humans” that the characters have lived up to the promise of the title, taken from the goal they’ve set for themselves to grow up, the film itself has and then some in how precisely and generously Leonard and a talented cast and crew have captured that being an adult can be as much about letting go as taking charge.

“Fully Realized Humans” does not yet have U.S. distribution.