Dir: Michael McCullers . US. 2008. 98 mins.

A smart comedy for adults, Baby Mama is a consistently funny pleasure, filled with charismatic performances and a nicely understated emotional element. Though superficially an Odd Couple-style look at two mismatched women - one hired to carry the other's child to term - this female-centred laugher mostly eschews caricature for warm, silly observations about grownup relationships.

After its premiere at the Tribeca Film Festival, Baby Mama opens in the US on April 25, targeting the date-movie crowd that might blanche at the R-rated antics of Harold & Kumar Escape From Guantanamo Bay, also opening this weekend. It will be intriguing to see if this Universal release will capitalize on the recent spate of blockbuster pregnancy comedies - Juno and Knocked Up, which both grossed about $219m worldwide - or if its narrative hook will now seem passe.

Stars Tina Fey and Amy Poehler both hail from Saturday Night Live and have previously held supporting roles in successful comedies. Fey's feature screenwriting debut, Mean Girls, opened in April 2004 and rode good word-of-mouth to a US tally of $86m, although that film was certainly helped by rising pinup Lindsay Lohan. As for Poehler, her highest-profile film appearance was in 2007's Blades Of Glory, which skated off with $119m domestically. Ultimately, Baby Mama's challenge will be to lure away enough couples from last week's Forgetting Sarah Marshall (also from Universal) and next week's Made Of Honor to find some box- office traction. Of the three films, Baby Mama seems most likely to benefit from strong reviews, which could be a major selling point for adult women.

Internationally, a lack of sure-fire names will certainly hurt, although this comedy's universal theme of the ecstasy and agony of childbirth will be a benefit. Regardless, Baby Mama could be a potent rental, especially if it gets muscled out of the theatrical marketplace by its comedy competition.

Kate (Fey) is a successful, thirtysomething single career-woman who is getting the urge to have a child. But after learning that she's infertile and that adoption might take up to five years, she hires a surrogacy centre that pairs her up with trailer-trash airhead Angie (Poehler). But once Angie and her boyfriend (Shepard) have a fight, she moves in to Kate's swanky apartment, forcing the two women to cohabitate as they wait for the birth.

On paper, Baby Mama feels like a broad comedy where uptight Kate and dim-witted Angie will eventually learn they have more in common than they first assumed. And while there are certainly jokes at the expense of both characters' class standings, the film largely succeeds in not basing its humour on such stereotypes.

Writer-director Michael McCullers, making his feature debut, worked as a gag writer on Saturday Night Live and collaborated with Mike Myers on the scripts for the Austin Powers trilogy. Despite that background in sketch comedy and broad spoof, though, McCullers' film maintains a steady comedic rhythm throughout its running time. Rather than feeling like a scattering of random gags held together by a slight narrative, Baby Mama's story nicely builds the two women's evolving relationship while also making room for well-drawn supporting characters like Kate's doorman (Romany Malco) and her potential love interest (Greg Kinnear). Furthermore, the script has a couple unexpected twists that take the comedy into interesting, more emotional territory without feeling mawkish.

Fey and Poehler are both terrific, displaying a strong chemistry indicative of their years working on Saturday Night Live together. Baby Mama represents, in some ways, a perfect vehicle for each comedienne's persona: Fey as the bright but insecure professional woman, with Poehler as the low-class, good-hearted simpleton. But when the film requires some pathos, both actors are equal to the task, delivering nuanced performances that are mainly very funny but also allow a little room for acceptable sentimentality.

Baby Mama stumbles in its final act when plot contrivances finally get the best of the film. Additionally, a birthing teacher (Siobhan Fallon) with an unfunny speech impediment takes up too much screen time and is the one glaringly broad performance in the piece. But the film's ability to juggle laughs and romance with intelligence is refreshing, turning a potentially one-joke premise into a deeply satisfying comedy targeted at grownups but with a winning silly streak underneath.

Production companies
Relativity Media
Michael s/Goldwyn

Worldwide distribution
Universal Pictures/UPI

Lorne Michaels
John Goldwyn

Executive producers
Jill Messick
Louise Rosner
Ryan Kavanaugh

Screen play
Michael McCullers

Daryn Okada

Production designer
Jess Gonchor

Bruce Green
Debra Neil-Fisher

Jeff Richmond

Main cast
Tina Fey
Amy Poehler
Greg Kinnear
Dax Shepard
Romany Malco
Maura Tierney
Holland Taylor
Sigourney Weaver