The estimable comic talents of Tina Fey and Amy Poehler are no match for the mighty force of Commercial Filmmaking. This is, at any rate, my chief response to Baby Mama, which drops those two in a gender-specific takeoff on The Odd Couple and proceeds to strangle everything about that idea that you'd want to see. Instead, we are presented with a needlessly convoluted storyline that feels like the work of a studio functionary with a checklist, making sure that the result would be optimised for greatest marketability, and gags that are studded on top like those flavorless little sausage balls that come on cheap frozen pizza. There is nothing within it that speaks to the personality of those who made it; its cold script echoes only with the clack of an actuary's keyboard.

The elegantly simple concept, which anybody who has seen the advertisements already knows: Fey plays Kate Holbrook, a businesswoman whose T-shaped uterus leaves her unable to conceive and whose petitions to adopt are constantly denied. Desiring a baby more than anything else in the world, she enlists Poehler's Angie Ostrowiski to be a surrogate mother. When Angie's slobby, brutish common-law husband (Dax Shephard) throws her out, the two women end up living together, and Kate's mirthlessly by-the-numbers life and approach to pregnancy is thrown against Angie's trashy tastes and television-fed intelligence.

Although that's not the freshest idea to ever come 'round the block, there are many things you could do with that concept to make something special. Unfortunately, writer-director Michael McCullers (whose hackular resume includes script duties on the latter two Austin Powers films, a stint with Saturday Night Live, and perhaps most damningly, Thunderbirds) is not interested in those things. Instead, Baby Mama unrolls like a perfect storm of focus-grouped situations and joke-writing by committee. That central conflict - you know, the one that gives the film its title - often takes a backseat to a superfluous and unsatisfying love story that apparently exists only because comedies about women need love stories; and even that isn't as important to the film as the subplot about Kate's job as VP of Development for Round Earth, a chain of organic grocery stores clearly intended as a parody of Whole Foods; though such a parody might be welcome, I'm not sure why it dwells in this film. Unless it's to explain why Kate has such an urgent desire to force-feed Angie high-nutrition organic foods. Surely, there was no more elegant way to introduce us to that detail.

I would not spoil the second-half of the film, but it's here that the script goes from clumsy to off-the-rails, first in a wholly contrived conflict that threatens to send the film into plot overload, then with a happy ending of such forced artificiality that even though I saw it coming from a mile away, I refused to believe until the end that it was actually coming. The worst part is, without that false conflict, there wouldn't have been any need for a fake happy ending; the plot was well on its way to providing a very fine happy ending all on its own.

At any rate, saddled with that kind of wandering screenplay, it's not surprising that the humor mostly fizzles. Comedy born out of cramped situations thus ever did come across as awkward and over-written, rather than spontaneous and witty. Fey, trapped in a humorless straight role, doesn't suffer much from the bland gags, but Poehler doesn't have it in her to milk humor out of a shockingly mean-spirited "dumb trashy blonde" character that seems out of place in a film that strives for warm uplift. As Fey's love interest, the militantly anti-Jamba owner of an independent smoothie store, Greg Kinnear is customarily adrift (the man has a certain charm, but has he ever been even a little interesting without a rock-solid screenplay). Without question, the comic highlights of the film come from two grizzled old vets, Sigourney Weaver as the owner of the surrogate agency and an uncredited Steve Martin, note-perfect as Kate's surreal hippie boss, graced with the finest dialogue in the film ("I will reward you with five minutes of uninterrupted eye contact").

It's not an evil film. There is a genial tone throughout that only really comes under fire when gags about Angie's supposedly hi-larious awfulness as a person come into the picture, and there actually are legitimate jokes that legitimately work. A healthy percentage of these ended up in the trailer. What really saves the movie from descending into the deep pits of terrible is that it's not trying very hard: while nothing is quite as wretched as comedy that isn't funny, most of Baby Mama is so light in its humor that it almost seems like it's not trying to be funny at all. There's not much that replaces that, other than an allegedly sweet tone which isn't really. It almost has the sense of being a stoner comedy, all about the laid back good-natured jesting, except nothing else about the scenario suggests that this was any kind of goal.

The leading ladies are both much better than this. Every week on NBC's 30 Rock, Fey proves that she can handle a whip-smart line of snark (many of which she writes herself), and Poehler's tenure on Upright Citizens Brigade and sparkling small roles in comedies as high as Arrested Development and as low as Blades of Glory leave no doubt to either her range or her timing. This just isn't the vehicle for them; it's a bit of studio-mandated pablum with all the sharp edges sanded off to make sure that nothing will stand between it and a modest box-office run. I choose to take the optimistic view: if this film does well at all, and demonstrates that Fey and/or Poehler can open a movie, perhaps the next time out the suits will trust them with something a bit more inspired, maybe with a script that Fey herself wrote. If that's going to happen, I hope it happens soon, because Baby Mama is no kind of movie to leave hanging out on the top of your resume like that.