How Common Are Cryptic Pregnancies and Why Do They Happen?

During a cryptic pregnancy, people are unaware that they're expecting until midway through the third trimester — or even later. Here's what to know about this rare medical issue.

Cryptic Pregnancy
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TikTok is full of anecdotes from people who didn't know they were pregnant until months after conception or, shockingly, even until they go into labor. This is commonly known as a stealth pregnancy or a cryptic pregnancy. Whenever one of the personal stories, posts, or videos gets noticed, the comments are flooded with messages from people who — understandably — have a lot of questions about what a cryptic pregnancy is, how it happens, how common the issue is, and more. If you too have questions you'd like answered, find more details about cryptic pregnancies below.

What Is Cryptic Pregnancy?

"A cryptic pregnancy is one that goes unrecognized for greater than [the first] 20 weeks of the pregnancy or until the time of delivery," says Karenne Fru, M.D., Ph.D., F.A.C.O.G., an ob-gyn and fertility specialist at Oma Fertility.

You may sometimes hear other terms used to describe the same phenomenon. "'Cryptic' and 'stealth pregnancy' can be used interchangeably," explains ob-gyn Cynthia Wesley, M.D. "Previously, the term 'denied pregnancy' was used, until [psychology professor] Marco Del Giudice brought attention to potential physiologic contributing factors. He coined the term 'cryptic pregnancy' in 2006." Those physiologic factors include irregular menstruation patterns or a history of infertility, which can lead the person to not realize they're pregnant.

As for what cryptic pregnancysymptoms to look out for, they will sound familiar if you've previously been pregnant or have learned about the experience of pregnancy. "The main symptoms are similar to those of any pregnancy and include nausea, sensitivities to foods or smells, fatigue, heartburn, and gas, for example," says Dr. Fru. "The loss of a period is the hallmark of most pregnancies, but cryptic pregnancies are less likely to have this symptom as some bleeding may occur — leading the pregnant person to believe that they are not, in fact, pregnant." While this bleeding is period-like, it is not a period per se.

If the symptoms are so recognizable, you might be wondering why the pregnant person doesn't associate them with pregnancy. "In the case of cryptic pregnancies, these symptoms tend to be dismissed or attributed to other causes," says Dr. Fru.

"Additionally, there may not be an appreciable change in appearance for the pregnant person, leading to lack of suspicion of pregnancy," says Dr. Fru. "Sometimes the fetus is smaller than average," explains Dr. Wesley. "There are times when the habitus [i.e., physical build] of the woman makes it difficult to see a pregnancy bump."

How Common Are Cryptic Pregnancies?

Mentions of cryptic pregnancies tend to fascinate audiences — as evidenced by those TikTok posts — so you may think that they're more common than they actually are. "Cryptic pregnancies are rare," says Dr. Wesley. "Research [from 2002] shows that around one in every 475 [pregnant] women are unaware of their pregnancy until they are past 20 weeks. Cryptic pregnancies that are diagnosed at the time of giving birth only occur in 1 in 2,500 women." So, while the latter instances are often the most talked about in the media, they actually make up a small proportion of total cryptic pregnancies.

What Are the Causes of Cryptic Pregnancies?

A slew of risk factors that may contribute to your chances of having a cryptic pregnancy. "Cryptic pregnancies are most prevalent among women with a history of infertility or irregular menstrual patterns," says Dr. Fru. "For the former, they may not believe they can spontaneously conceive and for the latter, ovulation is such an unpredictable event that they may not think much about missing a few months of periods." Plus, there can be spotting during early pregnancy, and the pregnant person may confuse the bleeding with a regular period. "Some women have actually taken a pregnancy test [that] was negative," notes Dr. Wesley. "It's important to remember that urine pregnancy tests can sometimes give a false negative result."

Those aren't the only people who can experience a cryptic pregnancy. "If they happen to be on oral contraceptives but missed a pill, for example, the continuation of hormonal contraceptive pills may mask pregnancy symptoms after conception," explains Dr. Fru. That's because contraceptive pills themselves sometimes cause side effects that are similar to those of pregnancy (such as nausea), she says. "Furthermore the cervix is irritable in some individuals with pregnancy so that they may experience episodes of cervical bleeding, especially after penetrative sex," adds Dr. Fru. "It is different from the uterine bleeding that birth control pills instigate, but both present as vaginal bleeding."

People who have just given birth may also be more likely to develop a cryptic pregnancy. "Women who are postpartum are also at risk if they have unprotected intercourse as they may resume ovulating a few weeks after delivery," says Dr. Fru. "Usually, in this case, being postpartum itself may cause the neglect [masking] of any new pregnancy symptoms until several months later."

There are demographic factors to consider too, as well as those related to mental health. "At least one study has identified that younger, poorer women under great mental strain may be most at risk of ignoring pregnancy symptoms," points out Dr. Fru. "Sometimes the stressors of life can lead to a woman being unable to accept the fact that they're pregnant." Note: This is the cause that led to cryptic pregnancies previously being referred to as "denied pregnancies," but it's easy to see how this term fails to capture the full picture.

Can a Cryptic Pregnancy Lead to Complications?

Often, people experiencing a cryptic pregnancy don't consult health-care providers about it until they actually learn that they are pregnant, which means that certain aspects of their and the baby's health are overlooked. And sometimes, even when they do consult a health-care provider, their symptoms may be explained away as something else, says Dr. Wesley. "Sometimes women can have more than one [health] problem and the pregnancy is not diagnosed," she explains.

"The major complication of cryptic pregnancy is the lack of prenatal care," believes Dr. Fru. "This often leads to low birth weight infants, which is not ideal."

Then there's the question of lifestyle habits that are known to promote a healthy pregnancy. "In addition, the lack of lifestyle modification that often comes with the identification of pregnancy means these babies may be exposed to alcohol, drugs, and cigarette smoke, which the pregnant person may have avoided had the pregnancy been recognized," adds Dr. Fru.

Once the pregnancy is identified, health-care providers generally take a number of steps to prevent complications where possible, incorporating necessary prenatal care. "Patients [also] receive mental health screens to make sure they get any help they may need," says Dr. Fru. "Social work helpers are also key, as they may provide resources for an unexpected delivery and set the parent-child dyad up for success."

Although cryptic pregnancies are rare, they are well-documented. Unfortunately, there are a number of physiological, psychological, and social factors that may cause some people to be at greater risk for developing one. However, learning about cryptic pregnancies can help you better identify the issue should the need arise.

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