Teenage pregnancy is no laughing matter. Usually. But, as he did with the underrated satire Thank You For Smoking, director Jason Reitman finds genuine humour in a potentially touchy subject.

For that he should thank blogger-turned-screenwriter Diablo Cody (a she) whose acerbic, young mother-to-be Juno MacGuff is the perfect fit for the scarily talented Ellen Page. In fact, Juno and Hard Candy’s angel of vengeance Hayley Stark could be sisters.

But where Hayley was a schemer, Juno is just a 16-year-old smart aleck whose stream of put-downs and wisecracks never slows... Not even when she discovers that she’s been knocked up by gawky running enthusiast Bleeker (Cera).

Getting freaky with Bleeker was her idea, so it’s not his problem. But after bottling it at the abortion clinic (“Babies have fingernails!”), Juno decides to go through the pain barrier and give it up for adoption.

Thankfully, her parents take the news on the chin. Dad (Simmons) is nothing if not pragmatic and stepmother Bren (Janney) is also 100% supportive, though she’ll give as good as she gets in the attitude stakes.

Juno and best friend Leah (Olivia Thirlby) soon find the ideal foster parents in the small ads. And while Vanessa (Garner) is nice, if a bit anal, Juno really clicks with her jingle-writer husband Mark (Bateman). But there are bumps ahead in every sense.

Like Candy’s Hayley, Juno’s adolescent smarts occasionally strain credibility, never being lost for words and holding her own in debates on obscure splatter horror movies, edgy rock music and other too-cool-for-school-abilia.

But, blunt, curious and like totally unready (“I’ve been dealing with issues beyond my maturity level…”), she's a 21st century teen, fo’ shizzle.

Savvy though it is, the film doesn’t break any new ground. With teenage girls coping with smalltown ennui and riffing on pop culture with older men who should know better, we could be back in Ghost World. Nobody could accuse John Malkovich’s Mr Mudd production company of being inconsistent.

What makes this the more appealing venture is its underlying warmth and truthfulness; Juno is anxious only that her baby should be loved… yet couples often use parenthood to cover cracks in their relationship.

Forget about cold feet; this is one little treasure you don’t have to wait nine months to see.

Elliott Noble