It came to light recently that America might be jumping into a new baby boom. Birth rates reached their highest point since the early sixties. One only needs to tool around places like Mall of America– where the wise pedestrian takes out a stroller collision policy – to see the new America emerging from the womb.

Hollywood, with the greatest demographers that wooden Keanu Reeves performances can buy, is naturally up with the curve. Which could explain why there has been a rash – ha! – of pregnancy comedies being dropped off by the stork at a theater near you.

This week it’s Baby Mama, which opened the Tribeca Film Festival and stars Saturday Night Live writer/performer Tina Fey in her first out-front role. This also happens to be the first female buddy comedy to be made in a long time (I can almost smell the Cagney & Lacey remake; lock up your daughters).

Playing a neurotic victim of a narrow uterine channel, Kate Holbrook (Fey) is an organic foods executive who sees baby faces everywhere. It’s starting to take over her life and her job, managing the company for a swim-with-the-dolphins eccentric (a scene-stealing Steve Martin. We don’t know celluloid is organic.) To hit the snooze button on the cruel biological clock inside, she throws her eggs and her money into a surrogacy clinic headed by the very fertile Chafee Bicknell (Sigourney Weaver).

The clinic head honcha in charge of matching mother and surrogate must have a real eye for comic premises. For the upscale and uptight Fey, he sends over an Odd Couple opposite by the name of Angie Ostrowiski (SNL’s Amy Poehler), an uneducated skank called with a smoking habit, a drinking habit, and probably other habits we don’t want to know about. Soon Fey is buying her health food and driving her crazy. Poehler is chomping on Cheetos and peeing in her sink.

And then, Heavens to Betsy, they’re forced to move in together! And then a man (Greg Kinnear) enters the picture! How sprouted, dehydrated, free-of-pesticide nuts! Baby Mama is not the mother of invention. It possesses a worn premise and conventional sketch-comedy mentality – ranging from the suspect relationships down to the comic timing. But it takes a worn premise and a conventional sketch mentality and at least fertilizes it with some funny lines.

Like some pregnancies, the cleverness of writer-director Michael McCullers’ writing (and the likely considerable improv) is unexpected. Like childbirth, much of the success has to do with the delivery. It’s good to see that Fey – maybe the funniest woman in the world – can not only write a line but hit one, as well. While the largeness of the silver screen makes Poehler’s talent seem as scrawny as her stomach, Fey seems at least comfortable in the expanded canvas. A star is born? Ask me later.