As long as children continue to be brought into the world, we will probably have stories about the joys and pains of pregnancy and parenthood. In “What to Expect When You’re Expecting” — which takes its catchy title from Heidi Murkoff and Sharon Mazel’s perennially popular handbook for moms-to-be — screenwriters Shauna Cross and Heather Hach juggle four tales of five couples facing what used to be called “blessed events.” Perhaps not unexpectedly for a movie addressing this topic, there are numerous mood swings along the way.

First up are Jules (Cameron Diaz) and Evan (Matthew Morrison); she hosts “Lose It and Weep,” a “Biggest Loser” knockoff, and he’s a dancer on “Celebrity Dance Factor.” They had hoped to keep their affair a secret, but when Jules wins the salsa competition — and loses her lunch — on live television, it’s only a matter of time before the whole world knows she and Evan have, shall we say, a spinoff in the works.

Moving on, we have Wendy (Elizabeth Banks), the owner of a boutique called The Breast Choice and the author of a picture book called “Milk It.” Just when she and ever-loving hubby Gary (Ben Falcone) have given up on trying to have a baby, Mother Nature smiles upon them. Unfortunately, Gary’s irritatingly jocund, extremely wealthy dad (Dennis Quaid) and his bubble-brained, 26-year-old trophy wife (Brooklyn Decker) are also in the family way, which intensifies Gary’s inferiority complex. Gary, by the way, was also once a contestant on “Lose It and Weep,” and what exactly does it say about 2012 America when almost one-third of a film’s major characters turn out to be pseudo-celebrities from reality TV?

To remind us that impending parenthood is not always a laugh riot, “Expecting” gets semi-serious with the case of Holly (Jennifer Lopez) and Alex (Rodrigo Santoro), who dream of adopting an infant from Ethiopia. For an extra touch of drama, there’s the roller coaster relationship of Rosie (Anna Kendrick) and Marco (Chace Crawford), rival food truck operators whose one-night-stand leads to potentially long-term consequences. This is the most emotionally complex of the episodes and, regrettably, the one that gets the least screen time.

“Expecting” rotates between stories, “Love Boat”-style, and while none of them are terribly enthralling, by the same token none is so insufferable that you’ll want to rush for the aisle. Up until the requisite, predictably puerile delivery-room-freak-out sequence, director Kirk Jones (“Waking Ned Devine,” “Nanny McPhee”) brings a gentle, breezy touch to most of the material. Diaz and Lopez give appealing performances — this is certainly a far less painful experience than Lopez’s previous baby-themed vehicle, “The Back-Up Plan” — while Banks and Kendrick build reasonably multi-faceted characters that transcend the sometimes corny situations in which they find themselves. As Wendy’s spacey assistant, Rebel Wilson hits some enjoyably zany notes, and former “Facts of Life” star Kim Fields makes the most of a brief scene as the humorless social worker who sizes up Holly and Alex.

Aside from Quaid’s energetic take on an aging champ, the men don’t fare as well. While Chris Rock works overtime trying to steal the show as the chattiest member of a band of stroller-pushing dads known as the “dudes’ group,” his supposed zingers don’t have much zip. Rock may have had great expectations, but what you should expect from "Expecting" is a standard-issue date movie, complete with all the usual chuckles, tears, manufactured crises and comforting messages.