The elevator pitch for “Bridget Jones’s Baby” was probably, “Let’s prove that we can be funny even without Hugh Grant.” And although the third installment in the slowly gestating 15-year-old series feels a bit awkward without its traditional third wheel, it remains a decently pleasing multiplex sex comedy. If you enjoy British absurdity laced with a large ratio of obscenity, it’s an exhilarating geyser of tastelessness.

Here we catch up with our no longer youngish heroine, played by no longer youngish Renée Zellweger, who remains an exuberant font of potty-mouth jokes and bittersweet romantic comedy. Boyfriend never obtained, Bridget continues her long singleton phase, with spinsterhood not far off. She lives in a claustrophobic efficiency apartment full of ugly bric-a-brac that seems to mock her unfulfilled utopian fantasies. The most satisfactory parts of her life are her endless access to chardonnay, and her career as a TV news producer.

Unfortunately, her new boss is an arrogant hipster gargoyle (played to the hilarious hilt by Kate O’Flynn). She stares down the staff and free-associates gibberish ideas to replace the show’s attempts at journalism, which strikes me as a very relevant modern character type.

Bridget might have found solace with her old lovers, but they are unavailable. Her womanizing ex and former boss, Daniel Cleaver (played by Grant in the first two parts of the franchise), is, for colorful dramatic reasons, out of the picture. And her erstwhile fiancé, the ferociously reserved barrister Mark Darcy (Colin Firth), is inconveniently married.

Then fate and a face-first plunge into the mud at a music festival introduce the klutzy charmer to a potential backup. Jack Quant (Patrick Dempsey) is a dashing American billionaire thanks to his dating website, which juggles algorithms to reveal the client’s romantic ideal. Coincidentally, Jack and Bridget are a near perfect match.

She is soon headed toward a blessed event, with no idea whether the father is her new acquaintance or Darcy, who became her conquest for a day while his wife was away.

Zellweger is fine as the everlasting adolescent, even if it appears that her facial features don’t always conform to her emotions. Her vocal delivery resonates wonderfully, and she plays Bridget with a mix of cheerful facade, jokey pain and straight-ahead urgency that is inexplicably touching.

Firth shines, as always, in his trademark undemonstrative manner. Dempsey, who generally strikes me as an anonymous actor, is on target playing this savvy charmer, falling onto a funny rivalry with Firth over the coming baby’s paternity. And the film adds a couple of celebrity cameos to a large supporting cast of returning characters.

On its way to the requisite happy ending, the film jumps through plenty of outrageous, can-you-top-this? hoops. I especially enjoyed the lunacy of having the prim and proper Darcy in court arguing a case for a Russian feminist punk rock band that looks, and acts, a lot like Pussy Riot.

Even when the film doesn’t track logically — and often it doesn’t, laughs being the top priority — it’s entertaining. Like Bridget, it’s a mess, but an adorable one.