‘Baby Mama’: Fertility rites and wrongs

The premise for "Baby Mama" will click with those of us who remember Mary Beth Whitehead.

She was the surrogate mom who became a minor celebrity when she decided she wanted to keep her baby, prompting a legal battle that pitted her against the would-be parents. Attorneys argued contract law, but the real drama lay elsewhere: Whitehead was poor, the couple who hired her were rich (routinely described in the press as "yuppies"), and the case played out as a juicy class drama.

So does "Baby Mama," starring Tina Fey as a wealthy single executive who hears the alarm on her biological clock and rents the uterus of a poor woman (Amy Poehler). The two share an egg, and then an apartment.

Fey and Poehler, both vets of "Saturday Night Live" (ditto writer/director Mark McCullers) are funny as individuals, funny together, and they are fed enough funny lines to make "Baby Mama" work as breezy, lightweight entertainment (particulary when spitfire Poehler shows up).

So much so that you don't notice that the characters are actually caricatures, and off-putting at that — rich and smart, poor and ignorant.

It's often hard to buy Poehler — with her gym-perfect body and her natural hawk-eyed intelligence — as rent-a-mom Angie, who lives on a diet of junk food and junkier TV. It's a bit like watching Barack Obama try to bowl.

Drawling Dax Shepherd, a natural yokel, has better luck as Angie's Camaro-driving boyfriend, and there are other funny cameos — Sigourney Weaver is a highlight as an impossibly fertile older woman (she heads the surrogate agency) used as a foil to Fey's biological hard-luck.

"Baby Mama" works best when it's centered on the Odd Couple chemistry of Poehler and Fey. Some of the ancillary plot lines aren't so good — Fey's romance with the owner (Greg Kinnear) of a smoothie store is pretty flat, and exists mainly to serve up plot "twists" that you could spot coming over the Ben Franklin Bridge.

Which, incidentally, is a fixture in the movie, set in Philadelphia. A pregnant woman's mad dash to the hospital shows her leaving the city via the Ben Franklin, and ending up at the Hospital of the University of Pennsylvania.

The movie's like that: some weird detours, some dead ends, but it gets where it needs to go. *

Produced by Lorne Michaels and John Goldwyn, written and directed by Michael McCullers, music by Jeff Richmond, distributed by Universal Pictures.