I saw "The Back-up Plan" at a very special screening. On Venus, I believe. The audience was peppered with contest winners, brought in to catch a sneak peek and to fill the air with pre-sold laughter. And yet there's no denying that the women of all ages sitting around me genuinely loved this movie. They laughed all the way through it — laughed at the vintage corn (when was the last time a movie dredged up the old boy-girl meet-cute in a taxi they both think they've hailed?), laughed at the adorable little handicapped dog (a gag-on-wheels that was funnier in "Babe: Pig in the City"), and laughed long and hard at the shocks and wonders of pregnancy and childbirth with which the picture is centrally concerned. At the risk of sexist condescension, I'd say that being a woman — or a woman of a certain kind, anyway — is a crucial prerequisite for enjoying this film.

Jennifer Lopez, at her most appealing here, plays Zoe, the owner of a conscientious Greenwich Village pet shop — not a "puppy mill," as she disdainfully puts it, but a store that offers up proudly un-bred mutts for adoption. Despite her strong resemblance to Jennifer Lopez, Zoe has had no luck finding a good guy. Now, facing 40 and longing for a family, she's decided to have herself artificially inseminated. Mere moments after undergoing this procedure, she has the fortuitous taxi-cab encounter with Stan, who's played by Alex O'Loughlin, an Australian actor so appealing in his own right that he might as well have a "good guy" tag affixed to his wrist (or perhaps glued to his frequently shirtless chest). Stan is instantly smitten. He follows Zoe down the street and then down into the subway, where any New Yorker will be surprised to note that she doesn't call for a cop.

Zoe and Stan — whose crunchy vocation is creating artisanal cheeses at an upstate farm — are of course made for each other. They share their dreams. His is to open "a sustainable gourmet shop," although he's also studying economics on the side (a strained plot flourish). After some preliminary nuzzling, Zoe tells Stan she's pregnant by someone she knows only as a number on a sperm-bank shelf. Stan is taken aback, but not for long, and soon he's dealing with the complications of having (PG-13) sex with a pregnant woman, and with her impromptu vomiting and her hilarious inability to fit into her favorite clothes and her sudden lust for lapping up ice cream in bed. (There's also a bit in which Zoe, overcome by the aroma of a pot of tomatoey goop bubbling on a stove, submits to temptation and begins shoveling the stuff into her mouth with her hands — a scene that might best have been left in its entirety to the blooper reel at the end of the film.)

In addition, there are infusions of familiar wisdom from Zoe's tiresome grandmother (Linda Lavin) and a father-of-three (Anthony Anderson) Stan meets in a park. There's also one delightful line — when the slowly swelling Zoe tells Stan, "I miss my hot ass" — that will strike a special chord with Lopez watchers. Then there's a fateful penny that keeps turning up in an entirely rom-com manner, a drum-thumping single-mothers group ("We do what we have to do when we don't have a penis partner"), and a birthing scene in a wading pool that struck me as overbearingly grotesque, but which had the laughing women at the screening I attended laughing even harder.

"The Back-up Plan" was scripted by TV sitcom veteran Kate Angelo, and despite its obstetrical candor, it has a fabricated sitcom blandness. It seeks to take us to the heart of female functions; but it leaves the men in the picture with little to do but stand around looking love-struck, heartsick or, for the most part, clueless. It's not really a date flick. If anything, it's a girls' night out. Depending, as I say, on the girls.

Don't miss Kurt Loder's reviews of "Paper Man" and "The Losers," also new in theaters this week.

Check out everything we've got on "The Back-up Plan."

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