LOS ANGELES - There's a very visible baby bump on the set of "How I Met Your Mother," but no one's paying it much attention. In a flashback scene for a recent episode, the ever-present narrator's memory is lapsing and he can't recall whether Lily (Alyson Hannigan) was pregnant during the moment he's recounting. As Lily spars with Barney (Neil Patrick Harris), her burgeoning belly remains unmentioned, serving simply as a resting spot for a plate of Chinese food.

Now in its sixth season, the show is toying with the idea of employing a device much belabored in sitcom land: the addition of a baby.

A due date is still unknown - and for some fans, that's OK. Much of the appeal of the CBS sitcom has centered on the interminable mystery of whom Ted Mosby (Josh Radnor) will ultimately marry. But suspense can hold viewers' interest for only so long before it grows frustrating.

Baby talk has loomed over the series for a while, with longtime couple Lily and Marshall (Jason Segel) flirting with parenthood much of this season. And hints of a coming pregnancy stretch as far back as fall 2009, when, in a flash forward, Ted tells his kids how his friends quit smoking: Lily stopped once she started trying to get pregnant and Marshall quit when his son was born. Even if the stork doesn't drop by this season, it's fated to happen eventually.

"I think we'd be super cute with a baby," Segel said during a set break. "We'd be like those people in the photos that come in picture frames."

Still, the show's producers are proceeding with caution.

"There's fear: Will it limit us? Will the show lose something?" admitted executive producer Craig Thomas. "However, the idea of opening up whole other stories is exciting."

Of course, there's that teeny tiny issue of shark jumping: In prime time, infants have a mixed record.

Some lamented that Murphy Brown lost her snarky edge after she gave birth at the end of the show's fourth season. Others found that "Mad About You" got only more maddening after married couple Paul and Jamie welcomed a daughter near the end of the show's run. Then there was "Roseanne," which decided to add a fourth kid - named Jerry Garcia - to its household in its seventh season.

"I think it's thought of as a potential death knell to a show," Thomas said. "But at the same time, the series is all about growing up, so to not address it, to not see this couple who has been together since age 18 get to that point would seem dishonest."

The series isn't alone in its baby quest. Scour the television landscape and peewee youngsters are rampant. A little tyke was added this season to NBC's "The Office," shortly after Jim and Pam completed another TV convention - getting married. "Dexter's" bundle of joy came in the form of baby Harrison, while another Showtime series, "Weeds," shows Nancy trying to protect her newborn from his drug lord father. Fox's "Raising Hope" centers on a cherub-faced bambino.

CBS comedy "Rules of Engagement," now in its fifth season, is also feeling a bit fertile, with Jeff and Audrey Bingham (played by Patrick Warburton and Megyn Price) looking to conceive via a surrogate. It was a move that initially concerned Price.

"She was worried it might ruin the show," said creator Tom Hertz, who later added, "I looked back at every episode we've done and asked whether there were any episodes we couldn't have done with an unseen baby in the second bedroom. And there was barely any . . . The entire series doesn't have to suddenly stop because there's a baby - that happens in real life, not TV."

A visit from the stork is a ploy that dates to television's early years. "Mary Kay and Johnny," a late 1940s sitcom that followed the exploits of a young married couple, incorporated Mary Kay Stearn's real-life pregnancy and baby into the show. And then there was the famous birth of Little Ricky on "I Love Lucy."

TV historian Tim Brooks plays down the notion that adding a small child is a catalyst for a show's demise.

"It does two things: It gives the actors somebody to bounce off of, and it tends to bring in women, particularly younger women, which is who advertisers want to reach," he said. "It's a way of slowing the inevitable decline and erosion of a show. It all depends on how a show incorporates the baby."

Sometimes, the kid is added to liven up an aging cast. Angel Cohn, managing editor of the blog Television Without Pity, cited Seven ("Married With Children") and Emma ("Friends") as examples. But often the child gets lost in the shuffle. And there are inherent problems with baby characters: When they age rapidly over a short span of time, while other family members don't (as in "The Fresh Prince of Bel-Air," where Little Nicky aged from a baby to a preschooler in a matter of months).

"For it to work, it has to make sense," Brooks said.

With 100-plus episodes of "How I Met Your Mother" under her belt, Hannigan said the timing is logical for TV's loving married couple.

"I love that this show has always dealt with them as a real couple. Real couples at this point in their lives are either having babies or talking about having babies."

Thomas acknowledged that they considered bringing in the baby story line when Hannigan was pregnant in 2008. Hannigan, for one, is glad they opted against it.

"It was too soon," she said. "Just the vast amount of time we spend in MacLaren's [Pub] . . . it would really affect the baby. Oh, and the show."