Sometimes the LawOfInverseFertility hits so hard that the woman doesn't even realize she's pregnant, often not until the ScreamingBirth (and sometimes not even then). Cries of "ButICantBePregnant" and "how could I have missed this?" ensue. For whatever reason, when they ''do'' notice before giving birth, it isn't the lack of [[NoPeriodsPeriod periods that tips them off]], but rather the morning sickness and WackyCravings. It seems that heroines just don't keep track of their monthlies. Cue BabiesMakeEverythingBetter!

This is TruthInTelevision, in several ways.

* When they near menopause, women's periods can become erratic, making them more difficult to track. Couple this with the fact that menopause takes time and doesn't occur at the same age for every woman, and older women can have an unplanned child whose college years will coincide with their own retirement.
** Similarly some younger women can have health issues that make fertility unlikely or erratic.
* In many eras, sex education was non-existent or pathetic, and some young women simply ''didn't know'' the details surrounding pregnancy and its cause.
* Even for young, healthy, well-educated women, pregnancy can end up a surprise. Sometimes implantation of the embryo can cause minor bleeding and the woman can mistake that for her regular period. Read the [[note]]Roughly once a month, a woman's body builds a lining on the uterus to defend against the possibility of pregnancy. Human pregnancies are more invasive than most, a trait shared with other primates, some bats, and the elephant shrew. The shedding of this lining is menstruation (you may have noticed dogs and cats don't menstruate; in fact they and other placental mammals reabsorb the lining. So do human women, just not all of it). The embryo implants in this lining by using enzymes to dissolve a portion of it just a little bit. This can cause some spotting that, except for the amount of material, would be identical to menstruation.[[/note]] for more details. Or possibly the woman, like most women, leads a busy life and doesn't necessarily keep close track of her periods, relying on [[HystericalWoman the warning signs]] to keep from making a mess.

Not to be confused with ButWeUsedACondom, but it's likely to be a result.

'''Beware, all spoilers are unmarked.'''
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!!Examples:

[[foldercontrol]]

[[folder: Anime and Manga ]]

* ''GreatTeacherOnizuka'' -- Kunio Murai's AbsurdlyYouthfulMother didn't realize the implications of her sudden weight gain at first.
* In ''Manga/KodomoNoOmocha'' Sana's biological AbsurdlyYouthfulMother mom Keiko actually didn't know she was preggers ''until she gave birth''. Somewhat more understandable in the manga, where Sana's birth happened when Keiko was 14 (she's still very young in the anime, but not THAT much), and it's strongly implied than Sana is also a ChildByRape and the result of sexual abuse by Keiko's uncle.
* This happens to Shigeru in ''AkkanBaby'', though in her case it's not so much "ButICantBePregnant" as "how is babby formed?"
* This trope was played tragically straight in ''{{Berserk}}'', where Guts and a now insane Casca only discovered that she was in her beginning stages of pregnancy after she miscarried their child under the severe trauma that she sustained from the Eclipse [[note]]A few fans believe that Casca might have known she was pregnant before she went insane and either never got the chance to tell Guts or [[MySecretPregnancy didn't want to tell him]] out of consideration that he would stay with the Hawks out of duty instead of pursuing his dream[[/note]].

[[/folder]]

[[folder: Fan Works]]

* This trope shows up in the {{NGE}} FanFic ''Fanfic/TheSecondTry''. However, the "surprise" in this case is rather warped due to couple in question being ''[[DysfunctionJunction Asuka and Shinji]]''. Due to her mess of insecurities, Asuka was rather freaked out when she discovered she was pregnant and had tried to hide it from Shinji (She even went as far as to ''starve herself'' in a misguided attempt to induce a miscarriage). He only found out after a rat got into their trash and he stumbled onto a positive pregnancy test Asuka tried to hide. To say he was surprised would have been an understatement.
** Incidentally, Asuka avoids the usual markings of trope, as what tipped her off to her condition was missing one of her periods.
* In the backstory of Kyon's mother in ''Fanfic/KyonBigDamnHero'', it took a while for her to realize she was pregnant of Kyon due to a mix of ignorance and her lack of physical growth, compounded by a FriendlessBackground and a strained relationship with her parents.
* In the ''Franchise/SailorMoon'' story ''[[http://www.lethesbanks.com/BestFanfiction/mo_mscon.txt Misconception]]'', the plot is kicked off when Usagi learns about Chibi-Usa's previously-unmentioned older brother. One whose birthday is roughly eight and a half months away...
** As with the above mentioned Second Try case, it was only Chibi-Usa's comment that revealed it to Usagi. The ensuing nausea was from the shock and stress of learning she was going to be a mother far earlier than she realized, not morning sickness.
* In the ''Film/StarTrek'' fanfic ''[[https://www.fanfiction.net/s/9694363/1/Safe-and-Sound Safe and Sound]]'' we find out early on that Uhura is pregnant with Spock's child. She and the senior officers find out when the computer scans her and informs everyone (the biggest reactions come from Kirk and Scotty, the former spitting his mouthful of water into [=McCoy's=] face and the latter falling off his chair). This one is justified in that she was only one month along (before she would have noticed the missed period and before morning sickness came into play) and she and Spock didn't take precautions because of [[MateOrDie a certain incident which happens to Vulcans every seven years]].
* In chapter 62 of ''FalloutEquestriaProjectHorizons'', a medical scan during [[spoiler:a cybernetic upgrading]] reveals that [[spoiler:main protagonist Blackjack]] is pregnant. It comes as a particular surprise to her because she's still using a contraceptive implant. The medical ponies speculate that [[spoiler:Blackjack's {{Magitech}} cybernetics saw the implant for another piece of useable scrap material and absorbed it.]]
* Done more realistically in ''FanFic/MegaManReawakened''. [[spoiler: Tron Bonne]] finds out after 2 months of pregnancy, and tells the other characters soon after.
* Used in ''EggBelly'', when Setsuna gets pregnant by a girl. [[spoiler: (Apparently, Pactio sex can give even same-sex couples a child.)]] The scene where the doctor tells her this is hilarious.
* In ''Fanfic/ExtendedStay'', the Mistress and the Superjail crew find out she's pregnant just when Ultraprison is about to leave. This one is justified since she hasn't been far enough along to exhibit any symptoms.
* A minor character in ''Fanfic/RedFireRedPlanet'', Master Chief Special Warfare Operator Haellh, mentions to Admiral Riker early in chapter four that she's six weeks along. Her fellow fireteam member Petty Officer Freeman is really surprised by this and complains about her not telling him, but she says she only found out a few hours before.
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[[folder: Film ]]

* The Creator/MontyPython movie ''Film/MontyPythonsTheMeaningOfLife'', previous to the infamous "Every Sperm Is Sacred" song, featured a poor Yorkshire family whose mother was having babies drop right out from between her legs as she cooked and cleaned for her burgeoning family. This may also be implying that it's less that she didn't know and more that she didn't care, since they had dozens of children already.
* The new cute swimming instructor in ''WaterBoys'' discovers she's eight months pregnant and goes on a maternity leave immediately after managing to convince her five team members to throw away their pride and join her synchro-swimming team for her.
* Emmeline in ''TheBlueLagoon'' becomes pregnant with Richard's child and has no clue whatsoever until ''after'' she's given birth. She even tells Richard she doesn't ''know'' why she had a baby. Justified due to them having been living on the island since they were children and having no formal sex education whatsoever.
* It's unclear how long she knew about it, but ''[[Film/TheAddamsFamily Addams Family Values]]'' starts with Morticia announcing that she's going to have a baby...right now, and being rushed to the hospital for delivery. (The surprise is only within the context of this movie, though, as the SequelHook of the previous one had her wordlessly announcing said pregnancy by way of knitting baby-sized pajamas.)

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[[folder: Literature ]]

* In the satirical 'legend' of Pope Joan, a woman went to Catholic school disguised as a boy and worked her way through the ecclesiastic ranks to Cardinal and finally Pope. Her cover was blown when she put her foot in the stirrup to mount her horse and promptly gave birth before a shocked audience.
* In a subversion, Maya Angelou relates that she knew she was pregnant in ''IKnowWhyTheCagedBirdSings'', but the surprise was certainly on her family after she hid it from them for eight months.
* Implied in ''Discworld/TheFifthElephant''. Even if Lady Sybil wasn't surprised, [[CrowningMomentOfFunny her husband most assuredly was]], and his stupid questions and her dry responses are particularly [[HilarityEnsues hilarious.]]
* Daisy's mother in ''TheStoneDiaries'' is unaware that she's pregnant.
* Bluestar in ''[[Literature/WarriorCats Bluestar's Prophecy]]'', thanks to her one-night stand with Oakheart. She is unaware of her pregnancy until another cat points it out.
* A double-subversion from Literature/TheBible: Sarah has overheard three men (actually [[AngelUnaware angels in disguise]]) telling her husband that he and Sarah will have a son. She laughs because [[ButICantBePregnant she is old and has been infertile for a long time]], and gets [[WhatTheHellHero called out]] for laughing by the angels, which shuts her up. Sure enough, she does become pregnant, and she names her son Isaac (because she laughed at the prospect of having a child at her age, and boy was she wrong!)
* In ''Literature/KingdomOfLittleWounds'', Ava realized she was pregnant after Jacob had already left her. She insists that Jacob ejaculated on her stomach.

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[[folder: Live Action TV ]]

* This happened to Peggy Olsen in ''MadMen'', such that she didn't know until she ''went into labor''.
* Was a plot point on ''{{Eastenders}}'' a while back where a teenager gave birth not having a clue.
* Happened to an obese woman in a first-season episode of ''StElsewhere.''
* The aptly-titled ''I Didn't Know I Was Pregnant'' is about this. See the "Real Life" category for details.
* A fat woman complaining of severe cramps went into the ''{{ER}}'' and not only realized that she was pregnant but that she was giving birth to twins. Dr. Benton had to deliver the baby--something he "hadn't done since med school."
** Elizabeth Corday gets hit with this in the seventh season. Her response to the news was a flat "That's impossible."
* ''Series/DoctorWho'' Series 6 gives one to Amy Pond. The surprise element is made more plausible, so to speak, by having the Amy we see be a (non-pregnant) duplicate with her consciousness, while her comatose (pregnant) real body is elsewhere.
* Happened in the latest series of "Series/{{Whitechapel}}" when DS Miles' wife fears she might have ovarian cancer only for it to turn out she's 6 months pregnant
* At the end of "Baby on Board", ''ModernFamily'''s third-season finale, Gloria [[ConfessionCam tells us]] she had thought she was carsick but, no, she's really pregnant, as the camera shows her buying a pregnancy test kit
* Appears in the ChristmasEpisode of ''Series/CallTheMidwife''.
* A minor point in the fifth season of {{Castle}}. [[spoiler:Ryan and his wife are having trouble getting pregnant... because they're already pregnant.]]

[[/folder]]

[[folder:Music]]
* Averted in Music/EricChurch's "Two Pink Lines". The young man and woman in the story notice that the woman is two weeks late, so she takes a pregnancy test and the two of them angst over it. [[spoiler:The test comes up negative, so she leaves at the end.]]
[[/folder]]

[[folder: Theatre ]]

* In the stage play ''E/R'' (basis for the half-hour 1984 sitcom, not the hour-long 90's drama), a mother brings her teenage daughter into the hospital emergency room, complaining of "stomach cramps". The girl continues to deny she's pregnant even as she's giving birth.

* {{Played for Laughs}} in the stage musical of Roald Dahl's ''{{Theatre/Matilda}}'': Mrs. Wormwood is shocked to learn that she's pregnant, despite the fact that she (a) is nine months in, (b) is showing heavily, and (c) has been pregnant once before.

[[/folder]]

[[folder: Western Animation ]]

* In ''FamilyGuy'', Peter looks up one of his old girlfriends, who's turned ugly and obese in the intervening years. [[BlackComedy Then a baby splatters out from between her legs]], much to their mutual surprise. Though she then calls to her husband/boyfriend/lover/something offscreen "I ''was'' pregnant!" Implying that she did suspect, or was at least open to the possibility.

[[/folder]]

[[folder: Web Original ]]

* On ''TheGuild'', Clara was well aware that she was pregnant. Her husband, on the other hand, was quite shocked to find out.

[[/folder]]


[[folder: Real Life ]]

* TruthInTelevision: According to The Learning Channel series ''I Didn't Know I Was Pregnant'', women who tend to be a risk for surprise pregnancies often assume they were infertile, or [[ButWeUsedACondom think they used proper birth control]], or have such irregular periods that they didn't notice the pregnancy, or are so ignorant about the signs of pregnancy that she mistakes them for an illness. It can also occur in some women who suffer from illnesses that have symptoms that overlap pregnancy symptoms. They're so used to experiencing the symptoms as part of their normal life that there's nothing to tell them there's an additional cause for those symptoms. Some women still experience spotting during pregnancy (and thus think that they're still getting periods), while others don't even get a baby bump--not even nine months in--or have a larger body shape that makes small(er) fluctuations in weight and build hard to notice.
** One of the worst scenarios is when a woman is on birth control and gets sick and given antibiotics by their doctor and are ''not'' told by said doctor that antibiotics can make birth control less effective. As someone who only found this out through watching said show despite being on both birth control and given antibiotics multiple times, this is also TruthInTelevision, and a scary one at that.
* On either the same show or something similar, there was a story about a larger woman who had been thought to be infertile and thus didn't notice any of the regular signs of pregnancy. When she went into labor, she had been suffering from a bad case of constipation and thought she was trying to pass a bowel movement. The description she gives of what follows crosses the line from Nightmare Fuel into [[UpToEleven Nightmare Nitro]].
* A teen magazine once had a real life story about an 18 year old girl who hadn't gotten her periods yet. She'd had a boyfriend and hadn't used protection while sleeping with him because she didn't know that ovulation happens before the actual period comes. One day, ages after she and the boyfriend had drifted apart, she got some pretty strong stomach pains on and off. Thinking it was her first period, she just stayed on the toilet and ended up birthing a baby boy into it. The baby was okay, but her mother had to take care of him for a few weeks before the girl snapped out of her denial and started taking care of him herself.
* A story in relatively recent (as of September 2012) news was of a woman who did not know she was pregnant until she gave birth...in Afghanistan. ''In the middle of a war zone''. '''After serving as a bombardier in battle.''' (So she qualifies for PregnantBadass, even if she hadn't been aware of it.) Justified because the normal signs of pregancy (lack of periods, stomach pains, vomiting) can be chalked up to the stress of battle.

[[/folder]]

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