Cryptic Pregnancy: Causes & Symptoms

by John Staughton (BASc, BFA) last updated -

For some women, cryptic pregnancy is something that is both extremely confusing and worrying. While cryptic pregnancy is somewhat rare, it does require special attention, as a pregnant woman realizes of her pregnancy when she goes into labor.

What is a Cryptic Pregnancy?

Cryptic pregnancy is a situation in which a woman doesn’t know that she’s pregnant, often until after the 20th week of pregnancy. In some cases, a woman with a cryptic pregnancy doesn’t realize that she is pregnant until she goes into labor. There are a number of reasons why cryptic pregnancy can occur, and they are not inherently dangerous.

In some medical circles, this is referred to as a denial of pregnancy, but that doesn’t suggest a conscious denial by the mother, but rather a denial of the body when the amount of Human Chorionic Gonadotropin (hCG) is too low to be detected by a urine or blood test. [1]

A graphic displaying a pregnancy test

Pregnancy tests work by checking your urine. Photo Credit: Shutterstock

How Common is Cryptic Pregnancy?

Cryptic pregnancy affects roughly 1 in 500 women, but many other women may claim to have a cryptic pregnancy when they are not, in fact, pregnant. Many women experience common pregnancy symptoms, such as weight gain, hormonal imbalance, irregular menstruation, or cramping, and suspect that they are pregnant, but these symptoms are actually caused by another condition. On the other hand, some women with a cryptic pregnancy also may experience mild levels of these symptoms but assume that they are due to some other condition, due to the negative pregnancy test. [2]

Causes of Cryptic Pregnancy

Cryptic pregnancy can be caused by a number of factors, including the use of certain birth control methods, a recent pregnancy, high levels of stress hormones, low body fat, or polycystic ovarian syndrome, among others.

Recent Pregnancy

A recent pregnancy can cause hormonal fluctuations that may mask the presence of hCG in the blood and urine, resulting in cryptic pregnancy. [3]

Birth Control

Certain birth control methods release constant streams of hormones, which can fool the body into thinking that it isn’t pregnant, and even maintain somewhat regular menstruation. [4]

Stress Hormones

High-stress levels have been directly linked to cryptic pregnancy in the past, as this can also fool pregnancy tests and alter body chemistry.

Body Fat

Women with very low body fat often have hormonal imbalances, which make it difficult to detect the presence of hCG in the blood and urine. [5]

Polycystic Ovarian Syndrome (PCOS)

The cysts associated with PCOS can cause excessive release of hormones by the body, making it difficult to detect a pregnancy in formal tests. [6]

Symptoms of Cryptic Pregnancy

If you are experiencing a cryptic pregnancy, some of the most common symptoms include vaginal bleeding, ongoing menstruation, low birth weight, a lack of pregnancy symptoms, as well as mild forms of common pregnancy symptoms.

Vaginal Bleeding

While some vaginal bleeding is normal in women, unexplained spotting could be an indication of pregnancy but is often ignored by women who are convinced they aren’t pregnant.


In many cases, women will have irregular periods or mild menstruation throughout the course of their cryptic pregnancy, which convinces many women that they are not carrying a child. [7]

Lack of Symptoms

One symptom is a distinct lack of pregnancy symptoms, meaning no morning sickness, regular menstruation, low weight gain and no clear hormonal shifts. On the other hand, some women experience very mild symptoms of pregnancy and assume they are caused by something else.

How Long Does Cryptic Pregnancy Last?

In most cases, a cryptic pregnancy is detected at some point after the 20th week of pregnancy, when the symptoms of pregnancy become harder to miss, and your weight gain becomes more obvious. However, in many cases, cryptic pregnancy can last for your entire term, and a woman will be completely unaware that she is pregnant until she goes into labor and begins experiencing contractions. [8]


The most common side effects of such an unusual pregnancy include low birth weight, extended labor, and an abnormally long gestational period.

Birth Weight

Due to a lack of prenatal care and preparation, the birth weight of the infant is often low, and there may be a higher risk of birth defects, considering that women may not have followed a pregnancy diet, or engaged in other activities, such as alcohol consumption or smoking. [9]

Extended Labor

Labor pains and symptoms can last for an extremely long time before you actually deliver the baby – weeks or months, in fact. This can be painful and debilitating in many cases. [10]

Gestational Period

Your gestational period may be longer than average since the body doesn’t detect a fetus and therefore won’t put all the proper developmental processes in motion. This can result in gestational periods of 45 weeks or more. [11]

Cryptic Pregnancy Ultrasound

Many people are mystified by the idea of a cryptic pregnancy due to the accuracy of ultrasound tests. However, in the case of cryptic pregnancy, an ultrasound can fail to detect a growing fetus for a number of reasons, such as an excess of scar tissue, uterine introversion or a bicornuate uterus. [12]

  • Bicornuate Uterus
  • Tilted Uterus 
  • Scar Tissue 

Cryptic Pregnancy Labor

Labor for a cryptic pregnancy can be quite different than a normal delivery, namely because there will not have been much prenatal care and a lack of preparation for the eventual birth. Labor can be extremely long, with contractions and severe cramps beginning months before the actual delivery. For women who have no idea that they’re pregnant, this may be the first time they realize they are carrying a child. At this point, some doctors may recommend an emergency delivery of Cesarean section. [13]

While the physical delivery can be relatively short, the period before the birth can be highly stressful, uncomfortable and confusing. Women may experience abdominal pain, nausea, back pain, heart palpitations, blurred vision, cold sweats, diarrhea, fever and mood swings, among many others. These symptoms can last for days, weeks or even months before the delivery happens. Protection Status
About the Author

John Staughton is a traveling writer, editor, publisher and photographer with English and Integrative Biology degrees from the University of Illinois in Champaign-Urbana (USA). He co-founded the literary journal, Sheriff Nottingham, and now serves as the Content Director for Stain’d Arts, a non-profit based in Denver, Colorado. On a perpetual journey towards the idea of home, he uses words to educate, inspire, uplift and evolve.

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