What is Cryptic Pregnancy?

causes of cryptic pregnancy

Imagine going into labor and not even knowing you are pregnant. It’s called cryptic pregnancy and yes-it is possible.

Many women experience the symptoms of labor even before they receive a positive pregnancy test. Whether they have nausea, tender breasts or have missed a period; their bodies are giving them signals that they are indeed with child. 

But what if your body failed to send these signals and a pregnancy went undetected? While it seems like a storyline straight out of a movie it can and does happen to women all over the world. 

Cryptic pregnancy is a term that is used to define a pregnancy that goes unnoticed until delivery. Even though this sounds unrealistic it is possible. The Learning Channel (TLC) has a popular series called “I Didn’t Know I was Pregnant” where women share their stories of cryptic births. 

Some women featured on the series have larger frames so the body was able to hide a small bump. Yet even very slender women also were able to carry a pregnancy without noticing or showing! 

We asked one of our OBGYNs, DR Kate Killoran to share with us how this phenomenon happens and what could lead us to become pregnant without ever knowing it. 

What Causes a Cryptic Pregnancy? 

With a typical pregnancy, the newly fertilized egg first creates a blastocyst (a fluid-filled group of cells) that will develop into the baby’s organs and body parts.

About 10 to 14 days after conception, the blastocyst will implant in the lining of the uterus, called the endometrium. This can cause implantation bleeding in some women. It can be mistaken for a light period.

In a typical pregnancy, women will begin experiencing pregnancy symptoms around 4 to 6 weeks pregnant. 

According to a survey by the American Pregnancy Association:

  • 29% of women surveyed reported a missed period as their first pregnancy symptom
  • 25% indicated that nausea was the first sign of pregnancy
  • 17% reported that a change in their breasts was the initial symptom of pregnancy

With a normal pregnancy, once a pregnancy symptom is experienced, a woman can typically do an over the counter home pregnancy test and get a fairly accurate result. 

While false positives are not common, false negatives can happen. Testing too early, not following the instructions properly and certain medications can affect the results of the test. 

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Receiving a False Negative

A cryptic pregnancy, also called a stealth pregnancy, occurs when the body does not make enough of a hormone called human chorionic gonadotropin (hCG) to be detected using traditional pregnancy testing methods. 

When a woman is pregnant, the cells formed in the placenta produces hCG. This hormone can normally be detected in the blood or urine to confirm a pregnancy.

However, in a cryptic pregnancy, little or no hCG is detected due to the fetus not producing enough of this hormone. This would not last for long, maybe a few days, as even home pregnancy tests are quite sensitive to hCG. If a pregnancy continues to not to produce enough hCG the pregnancy would end in miscarriage. 

According to research, 1 in every 475 women does not realize that she is carrying a baby.  

Conditions that can Lead to a Cryptic Pregnancy

There are several conditions that could lead to a cryptic pregnancy. Some health conditions or birth control methods can lead women to believe that pregnancy is not a possibility. 


Polycystic Ovarian Syndrome (PCOS) is a common health condition that affects approximately 10 % of the female population. PCOS is caused by a hormone imbalance within the female reproductive system. 

It can cause many different symptoms including:

  • Excessive hair body hair growth
  • Loss of hair on the scalp
  • Persistent acne
  • Weight gain

PCOS also causes several issues associated with a woman’s reproductive cycle including: 

  • Missed periods
  • Heavy periods
  • Irregular periods
  • Infertility

Many women with PCOS may be told that a pregnancy without medical intervention could be difficult or even impossible. With this knowledge, along with irregular or even absent periods, women with PCOS could easily dismiss the signs of pregnancy. 

In addition, while PCOS does not have a cure, there are some lifestyle changes that can help with the symptoms associated with PCOS. Some lifestyle changes, such as weight loss or adopting a whole food diet, could trigger ovulation. 

If ovulation is triggered a woman could become pregnant and not know it. As she may not be expecting a monthly period, she may not discover or suspect that she is pregnant. 

Birth Control

Some birth control methods can give women a false sense of security. Some methods may cause an absence of a period or offer a high rate of protection giving women a false sense that they are unable to get pregnant. 


Barbara was 46 years old when she experienced a cryptic pregnancy. Barbara gave birth alone in a hospital triage to a 5 and a half pound son after labor pains and vaginal bleeding sent her to the ER. 

In the months leading up to her son’s birth, Barbara experienced fatigue, weight gain and missed periods. However, because Barbara had a tubal ligation procedure previously, she did not believe she could be pregnant. 

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I Didn’t Know I was Pregnant

A tubal ligation, also referred to as ‘getting your tubes tied’, is considered a permanent form of birth control. With this procedure the fallopian tubes cut, tied or blocked to prevent pregnancy. 

Tubal ligation works by either preventing an egg from travelling from the ovaries through the fallopian tubes or by preventing sperm from travelling up the fallopian tubes to the egg. Failure rates of tubal ligation are around 1.85%. 

Pregnancy after sterilization can occur years later. One case saw a pregnancy 23 years after the procedure. 

False Periods

Some women may mistake bleeding during pregnancy as a monthly period. Bleeding during the first trimester is fairly common. 20 to 30% of women experience some bleeding in their pregnancy. 

Bleeding during the first trimester can be attributed to implantation bleeding, infection, or changes to the cervix that causes bleeding after intercourse. 

As the pregnancy continues, bleeding is less common and can be a sign of a pregnancy complication. If you are experiencing bleeding in pregnancy it is important to speak to your doctor right away. 

I Didn’t Know I was Pregnant

Manon, a French Canadian flight attendant had been taking birth control pills faithfully for five years. She began experiencing some pregnancy symptoms such as being tired, feeling run down and a small weight gain. Yet she wrote the symptoms off as a side effect of a physical job and poor eating habits. This was possibly because she also felt that she was experiencing a monthly period. 

Even upon calling 911 after experiencing the first stages of labor, Manon was told by paramedics that she likely had kidney stones. It wasn’t until her water broke in the hospital that she learned she was pregnant. 

Manon mistakenly believed that bleeding during her pregnancy was her monthly period. With this regular bleeding and a busy lifestyle, she was able to ignore the other signs that pointed to a possible pregnancy. 


Some women falsely believe that they are unable to get pregnant past a certain age. A female’s chances of pregnancy do decline as she ages. 

Lisa always wanted children but as she neared 40, believed she was no longer fertile. She did not use any protection when she met a new partner. 

Shortly after meeting her new partner she made a career change which put her under extra stress. She began emotionally eating unhealthy foods and increased her smoking habit. 

She noticed weight gain in her stomach, but falsely believed it was due to her fast food habit. After realizing she has missed a few periods she took a pregnancy test. It was negative. She assumed she was perimenopausal. 

A few months later she realized it had now been six months since she had a period. She took two more pregnancy tests. One was inconclusive and the other was negative. Despite the weight gain and missed period, she believed she could not be pregnant due to a lack of ‘traditional’ pregnancy symptoms. 

I Didn’t Know I was Pregnant

At 32 weeks gestation, Lisa experienced a placental abruption which caused excessive bleeding. A placental abruption is the premature separation of the placenta from the uterine wall. This is a serious pregnancy complication that can cause stillbirth. 

The placental abruption may have been due to Lisa’s smoking during pregnancy. Many studies have shown a link between smoking cigarettes and placenta issues such as placenta previa (where the placenta covers the cervix) and placental abruption. 

Lisa’s son was born weighing 4lbs, 4oz. According to the American Pregnancy Association, smoking during pregnancy can prevent your baby from receiving the nutrients they need to grow properly. Having a smaller baby may have contributed to Lisa’s inability to realize she was pregnant. 

What are the symptoms of a Cryptic Pregnancy?

The symptoms of cryptic pregnancy would be similar to those you would experience in normal pregnancy but they may be more subtle. For instance, you may experience nausea and vomiting but it may not be as intense as experienced in a regular pregnancy.  Similarly, the baby’s movements can be mistaken for gas bubbles. 

Some women also experience period like bleeding during the pregnancy with shorter durations and lighter flow. Such a situation can make anyone think that they’re not pregnant.  

In addition to this, the other symptoms that you can experience include fatigue, food aversions, the need to urination more often, increase in weight, and feeling aches and pains in the body.

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Are Cryptic Pregnancies Different than Regular Pregnancies? 

These are possible reasons that enable women to ignore the obvious but certainly not always or even usually the case. Pelvic bone structure is different for different women some women don’t show as much as others but it is obvious when the truth comes out. With the possibe exception of very obese women. Usually, in case of such a pregnancy, the fetus is nested at the back of the womb, closer to the spine. Hence, the belly growth is slower and not as prominent as it would be in a regular pregnancy.

Secondly, the development of the baby is delayed in case of a cryptic pregnancy. As the baby is growing at a slower pace, the outer appearance of the belly is also affected.

I Didn’t Know I was Pregnant – Is that Unusual?

Though it is highly unlikely, research shows that it is possible. You may be unaware of a number of reasons. HCG in a pregnancy that would result in a live birth, even one that is small for gestational age, should have a positive pregnancy test. The only time a pregnancy would not be positive is in the first few days up to maybe a week.

The pregnancy test is either defective or the women is using it as directed. Low hCG means that your pregnancy tests will come back negative and as the fetus is positioned near the back of the spine, it is also easy to miss it on ultrasounds. Any experienced ultrasonographer would not miss a pregnancy after 6-8 weeks. The fetal position near the back of the spine after the first trimester is easily seen on ultrasound. 

Women may also be failing to seek medical attention or brushing off their symptoms. One study looked at the reasons that people avoid seeking medical attention. Among the answers were the high cost of medical care (24.1%), no health insurance (8.3%), and time constraints (15.6%). 

Regular Menstrual Cycles During Pregnancy?

Secondly having a regular menstrual cycle can be misleading as well. Even though the flow and number of days may be lesser but it’s natural to not expect pregnancy to happen when your monthly cycle seems regular. Same goes for birth control methods. If you are on birth control pills, for instance, a pregnancy doesn’t seem very likely.

Even though cryptic pregnancies are quite rare but they do happen. If you feel that you are experiencing any of the symptoms shared in the article, it’s good to err on the side of caution and consult a doctor.

It is possible to miss the signs and symptoms of pregnancy but the biggest reason for this is denial.

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