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- A cryptic pregnancy happens when you don't realize you're pregnant until at least 20 weeks.
- This can happen due to a lack of symptoms, irregular periods, birth control pills, and more.
- Cryptic pregnancy is rare and occurs in about 1 in every 475 pregnancies.
- Visit Insider's Health Reference library for more advice.
"I Didn't Know I Was Pregnant" isn't just a reality tv show – it's a real phenomenon. While rare, it's completely possible for someone to be unaware that they're pregnant until late into term or even until they go into labor.
This is called a cryptic pregnancy. Here's what you need to know about how often they occur and what causes them.
Understanding cryptic pregnancy
For the most part, women with cryptic pregnancies discover they're pregnant after week 20. This happens in about 1 in every 475 pregnancies.
"I have seen it for sure, but it's not incredibly common," says Dr. Christine Greves, OB-GYN at Orlando Health Winnie Palmer Hospital for Women and Babies. "They can go through basically half of their pregnancy and not know it."
However, there are rarer cases of cryptic pregnancies – about 1 in 2500 pregnancies – where someone doesn't realize they're pregnant until they are literally about to give birth.
While it may be hard to imagine how somebody couldn't realize they're pregnant, there are many reasons why cryptic pregnancies can happen.
What causes a cryptic pregnancy?
- Lack of symptoms: "Sometimes women do not have pregnancy symptoms. Some are blessed with not having nausea, vomiting, breast tenderness, and fatigue," Greves says. "Sometimes if a woman is overweight, she may not notice the weight gain [associated with pregnancy]." In this case, the person may not "show" as much. Additionally, a 2007 study published in Medical Hypotheses noted it's common for cryptic pregnancy babies to be underweight, which may also lead to less abdominal growth during pregnancy.
- Irregular periods: Irregular periods can make it difficult to figure out if you've missed a period or not, Greves says.
- Infertility: Alternatively, someone may be struggling with infertility, and think pregnancy just isn't a possibility for them.
- Birth control pills: If you miss a pill or take a dose too late, it's possible that you can ovulate, and that's how you can get pregnant on the pill in the first place. "Birth control pills can fail, and if you're taking them continuously, you may not have symptoms that would point out something is off," Greves says.
- Inaccurate pregnancy test results: Another thing that can fail? Pregnancy tests. Pregnancy tests can be extremely accurate, but only if you take them correctly. If you take them too early in your pregnancy, check the results too soon (or too late), or if your urine is diluted because you're well-hydrated, this can increase your risk of an inaccurate result. Specifically, a false negative result, which is when the results are negative but you actually are pregnant.
- Psychology: Furthermore, there may be a psychological component, where the pregnant person is so stressed or fearful about being pregnant to the point where they may experience full denial that they could be carrying a baby, according to the Journal of the Royal Society of Medicine study.
Insider's takeaway
Cryptic pregnancies are relatively rare. However, there's no research to indicate whether certain people are more prone to cryptic pregnancies than others, or if there are factors that increase your risk of having a cryptic pregnancy.
So for now, as far as we know, "No one is immune," Greves says.