J-Lo's new romantic comedy -com hits theaters

(NBC) - In "The Back-up Plan" Jennifer Lopez plays Zoe, a New York pet-shop owner who can't find the right guy, but decides to go ahead with her back-up plan and have a baby anyway, courtesy of an anonymous sperm donor.

Wouldn't you know it, the moment she gets pregnant with twins, she meets the right guy.

His name is Stan, he's played by the Aussie newcomer Alex O'Loughlin, and he's an upstate dairy farmer who sells his delectable goat cheeses at the farmer's market.

For a moment or two in the culture, becoming a single mother seemed a hip thing to do, especially if you were a celebrity, but the current economic climate only highlights the challenges for women who want to have kids on their own.

"The Back-up Plan" is a romantic comedy caught between those two visions of single motherhood.

Since Zoe is played by J. Lo, she is radiant and silky, beaming with personal power.

Yet as soon as she meets Stan, it's clear that getting pregnant on her own was not a good idea.

Even as the movie is satirizing Stan's anxieties about fatherhood, it seems to tiptoe around the real issue, that fatherhood might have been a little more inviting to Stan if he were, you know, the biological father.

As a romantic comedy, "The Back-up Plan" is friendly, but also fairly drab.

Its true subject isn't love but the comedy of pregnancy.

Zoe joins a support group for single mothers, and the movie features a home-birth sequence that's a funny, up-to-the-minute explosion of feminine energy.

We're supposed to believe that Zoe keeps pushing Stan away because she's scared of depending on him, but really, with this nice-guy hunk around, does she really want to raise twins on her own?

Too often, "The Back-up Plan" makes having it all look like something to complain about.

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