Any woman who doesn’t want to be Tina Fey is either lying to herself or not watching enough 30 Rock. The whip-smart, lovely and funny writer-actress has been on a charm offensive against America since 2004, when Mean Girls turned out to be far wittier than any high school comedy had a right to be. Now the sexiest glasses-wearer since Clark Kent may be ready to hit the big time thanks to her first starring role in Baby Mama, which isn’t quite as funny as what Fey writes for herself, but not a bad substitute either.

Fey stars alongside her former “Weekend Update” co-anchor Amy Poehler as Kate, a single career woman who, at 37, decides it’s time to have a baby. Forced to choose a surrogate when she discovers she’s infertile, Kate teams up with Angie (Poehler), an obnoxious hick from the wrong side of town who is in the whole surrogacy thing with her common law husband Carl (Dax Shepard) for a quick buck.

Before too long, though, Angie has run out on Carl and shacked up with Kate, who is frustrated not only by Angie’s junk food addiction and messy habits but by her refusal to “take care” of the unborn baby, at least according to Kate’s yuppified, organic-food-only point of view. As Kate stretches her prim lifestyle to accommodate Angie, she also finds time for Rob (Greg Kinnear), a smoothie store owner who is suspicious of the organic food grocery store Kate works for, fearing Kate is the face of neighborhood gentrification. He’s right, of course, but that doesn’t keep them from starting a tentative romance.

Baby Mama is formulaic enough that from the moment Rob and his dimples show up onscreen you know where his story is headed, and even Angie’s inevitable “betrayal” of Kate (you know, to make the story longer than a half-hour) feels predictable. But the delight is in the details, from Fey and Poehler’s warm rapport together right down to each of the supporting characters. Sigourney Weaver is hilarious and smug as the surrogacy specialist, pregnant in her late 50’s, and Romany Malco essentially reprises his motormouth character from The 40-Year Old Virgin-- luckily, it’s still funny. Steve Martin, though, is probably the best as Kate’s boss, making a believable character out of what could be the tired shtick of a New Age wingnut.

Though it stars two women and is about pregnancy, Baby Mama is not the standard chick flick—getting a man is not the be all and end all for any character, and you get the feeling that, by the end, Kate and Angie would be just as happy spending time together as going on any date. But it is a Hollywood comedy, and Baby Mama sticks a little too closely to the rules, especially given what we’ve come to expect from Fey and Poehler in their other work. Slow in some parts and hilarious in others, Baby Mama is nothing brilliant, but it’s an above-average comedy that makes better use of funny women than virtually any other movie has in years.