Chemistry can count for a lot in romantic comedies, especially these barren days. Chemistry isn’t really the problem here, but rather the material at hand. “Inspired by” a popular 1984 pregnancy guidebook of the same name, “What to Expect When You’re Expecting” is “He’s Just Not That Into You” if those characters wound up preggers. Directed by Kirk Jones (2009’s “Everybody’s Fine”), this is another star-topped comedy that intertwines various relationships faced with the joys and fears of impending parenthood. It’s not unpleasant or unentertaining to watch, but has nothing new to say and simply goes through the motions.

Live on the fifteenth season of a “Dancing with the Stars”-type show, TV fitness guru Jules (Cameron Diaz) realizes she’s pregnant with dance partner Evan (Matthew Morrison). The rest of the characters, residing in Atlanta, are connected by watching Jules on “Celebrity Dance Factor.” Wendy (Elizabeth Banks), an author and owner of The Breast Choice boutique, has been trying to have a baby for two years with her dentist husband Gary (Ben Falcone), until they finally get a plus sign. Freelance photographer Holly (Jennifer Lopez) is ready to adopt an Ethiopian baby with music-business husband Alex (Rodrigo Santoro) who’s getting cold feet over fatherhood. College-aged Rosie (Anna Kendrick), a food-truck chef, reunities with old high school flame Marco (Chace Crawford), who also runs a food truck, and a casual hookup leads to pregnancy. When Gary and Wendy share their happy news with Gary’s alpha-male NASCAR-driving father Ramsey (Dennis Quaid), he one-ups his son once again: his perky trophy wife Skyler (Brooklyn Decker) also happens to be expecting…twins! Of course, everything comes to a head (or, out comes a head) at the same Atlanta hospital on the very same night.

Using the non-fiction books by Heidi Murkoff as a springboard, screenwriters Shauna Cross (2009’s “Whip It”) and Heather Hach’s (2003’s “Freaky Friday”) script only finds a few real truths in this material without digging too deep. The rest is a frothy, commercially viable sitcom that wants to please the masses, but it’s only occasionally funny on the comedy front. Fortunately, Jones fleetly hops from expectant couple to couple and competently manages some of the tonal shifts.

The impossibly good-looking cast does fine, unchallenging work with what they have, but none of their characters are developed as more than likable, bland types. As the type-A Wendy, Banks nails all of the hormonal, vulnerable changes that a woman experiences when carrying a fetus. She becomes so overwhelmed that she can’t control her shrieky tantrums and flatulence. Falcone (Melissa McCarthy’s husband from “Bridesmaids”) is also quite funny. Diaz and Morrison play off of each other well as the celebrity couple, and both get to dabble in some “Biggest Loser”/”Dancing with the Stars” parody. Lopez and Santoro make a nice couple, and the adorable Kendrick and hunky Crawford share chemistry as the youngest couple. Quaid (not an actor prone to comedy) and Decker (showing what else she can do besides playing a swimsuit-with-legs in “Just Go with It”) also seem to be having fun.

As Wendy’s store employee Janice, Rebel Wilson (who, as Kristen Wiig’s strange roommate, memorably poured peas on her bleeding Mexican Drinking Worm tattoo in “Bridesmaids”) steals the show every time she’s on screen. Her presence is unfettered and her delivery acerbic. She’s so out there that somebody better give Wilson a one-woman show. And when she’s not in a scene, the “dude group” (Rob Huebel, Chris Rock, Amir Talai, and Thomas Lennon) bring the funny. When Holly senses her hubby’s reluctance to be a father, she sends Alex to the “dudes,” a gang of dads who parade through the park with their kids in tricked-out strollers and share their fatherhood truths. “Last week, my kid ate a cigarette,” one says, but they tell Alex not to judge in their dad circle. One almost wishes the film revolved more around these guys, especially Rock (a real daddy who knows a thing or two), since that’s where most of the energy goes.

The buff Joe Manganiello (HBO’s “True Blood”) also appears with these dudes on occasion, playing their bachelor idol Davis that jogs around the Atlanta park, but mostly stands around with his shirt off or does pull-ups with one arm. Also turning up in small roles are Wendi McLendon-Covey (the third “Bridesmaids” co-star to turn up here) as Holly’s friend, who only gets a few amusing quips, and the invaluable Megan Mullally, playing herself as Evan’s next TV dance partner, gets in a circumcision joke.

With the promising line-up of attractive, appealing stars, you’d expect “What to Expect When You’re Expecting” to fire on all cylinders. Had the script been polished and punched-up, the film might have been more than formulaic and merely adequate. Cute at best and shallow at worst, it gets points for not being just another bubble-headed Garry Marshall-helmed vanity show, though. Expect the bare minimum of a glossy studio comedy and that’s all you’ll get.

Grade: C
110 min., rated PG-13.

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