Obvious Pregnancy

""Dad said we'd know if Mom was having a kid because she'd look like a hippopotamus with a gland problem.""

- Calvin, Calvin and Hobbes, by Bill Watterson

One of the characters is pregnant. Right around the time she learns she's pregnant, she gets as big as a house - even if she learns almost immediately after conception. It's Rule of Perception - we can't be sure she's pregnant unless she's showing, can we?

There are other signs as well, ways to tell us that her increased size is due to pregnancy and not simple weight gain. Strangely enough, this will probably include eating, if only the classic ice cream sundae with pickles. She may have morning sickness soon after she learns she's pregnant, depending on the stomachs of the creators, but this rarely lasts. She will get moody.

Often accompanies But I Can't Be Pregnant or But We Used a Condom. Sometimes used to accompany an actress' real life pregnancy, which may account for some of the size so soon.

The opposite is Hide Your Pregnancy.

Anime & Manga

 * In Hell Teacher Nube, chapter #220 ("Izuna Becomes A Mother!?") greedy amateur exorcist Izuna dispels a weak cat Henge who is haunting a full-term pregnant mother, but accidentally displaces her Boze (the spirit of her unborn child), which promptly takes refuge inside of Izuna in order to shelter from Youkai known as Boze-Eaters, causing her to look ready to give birth herself. Given what Boze-Eaters look like, it's not surprising that it refuses to leave her until one shows up and scares it so badly it flees from person to person, each of whom looks heavily pregnant while possessed as well.
 * In Doctor Slump, this not only happens to Midori Yamabuki, but is actually lampshaded when Senbei promptly freaks out over her apparently abnormal development and gives her medical examinations to see if there's something strange going on. Well... stranger than usual, anyway.

Comic Books

 * The DC Comics Chinese "super-functionary" Mother of Champions lives this trope. Then again, her metahuman power is the ability to conceive, safely carry and deliver inhumanly large litters of children (up to twenty five babies in one pregnancy), and a secondary power is that gestation, from conception to birth, takes only three days.
 * In The Thrawn Trilogy comics, this is both used and averted. Leia Organa Solo is pregnant until fairly early in the third book. In Heir to the Empire this isn't exactly evident, even when she's in basically a bra and panties. In Dark Force Rising, she's showing. Explicitly said to be a month later, in The Last Command she's very pregnant before she gives birth. Part of this can be chalked up to the fact that each book was penciled by a new artist.
 * Ultimate Hela, after Thor knocked her up as part of their deal. Made more obvious by her Stripperific outfit. Somewhat justified by the fluid nature of time in the underworld—even though Thor thought the conception had only happened the night before, enough time has passed in the afterlife that Hela is already in her last trimester.

Live Action TV

 * Inverted on Charmed with Piper's first pregnancy, where people started complaining she took too long to show. Piper's second pregnancy goes right from conception to six months (to accommodate Holly Marie Combs' pregnancy)
 * On Scrubs, Jordan blew up at only four months, and later in one of JD's fantasies ate an entire goat as a Shout-Out to Jurassic Park.
 * As a Running Gag on The Cosby Show, Dr. Huxtable's patients frequently included pregnant women who'd dreamt of lashing out at their husbands.
 * Janice on Heroes, though the actress was pregnant in Real Life. It was a total coincidence that they got the idea for the character around the time she was starting to show...
 * That must be the case for many long running shows, such as soaps.
 * On ER, the pregnancies of two actresses were incorporated into the show. Problem is, both actresses were quite far along at a point where their TV pregnancies hadn't even been disclosed or discovered, so both of them still had to conceal their developing tummies until this time.
 * Averted in Glee. The pregnant teenager is only about 3 months in and as in real life, is barely showing.
 * It could have just been that we'd skipped ahead a month or two, but on Stargate Universe, an episode or two after T.J. reveals she's pregnant, she goes from not showing at all to obviously pregnant, then stays at that size until that plotline wraps up.
 * Averted with Scully's pregnancy on The X-Files, who didn't show until after the teaser in "Deadalive", roughly seven months into her pregnancy. Before that, there were scenes of her noticing the change in her body, but it wasn't noticeable to anyone else. She successfully hides her pregnancy from everyone (except Skinner) for months.
 * On Degrassi, Jenna actually starts showing a few weeks before she finds out she's pregnant (at first, she thinks she's just getting fat). However, this is justified — she doesn't realize she's pregnant until she's six months along.

Video Games

 * In the last few seconds of the ending cutscene for First Encounter Assault Recon 2: Project Origins, Alma is shown heavily pregnant, even though the "conception" occurred only seconds ago. Then again, this is possibly a psionic projection and thus her immediate development could be an illusion she is using to show her unwilling lover that she has become pregnant.
 * In Sam and Max: The Devil's Playhouse: The City That Dares Not Sleep, Sybil Pandemik returns from her honeymoon sporting one of these. She had been gone for nearly a year of in-game time, at least.
 * Ken's wife Eliza in the IV game. She graduates to Hot Mom when she gives birth to Mel in SSFIV.

Webcomics

 * Sabrina Online: Amy gets pregnant in February 1997, but due to the fact that the comic is only updated once a month, the progression of time is slowed down a lot (she doesn't go into labor until October 1999 and the baby isn't delivered until December). In August 1998, the artist apparently got bored of easing into it and jumped straight into making her very visually pregnant. Lampshaded in the strip.
 * In Wooden Rose, Nessa's pregnacy is blatantly obvious, making the doctor say she must be four months pregnant and causing Lillian to exclaim that she hadn't known him that long. However, her pregnancy reaches full term in a week.
 * Invoked in Goblin Hollow: the goblins are surprised but that's because they haven't noticed it's been eight months.

Western Animation

 * Subverted with Luann on King of the Hill who never showed until the episode where she gave birth.
 * Mrs. Gloria Duwong from The Weekenders was obviously pregnant for just about the entire series.