Though it might seem like the simplest thing in the world (after all, it is the backbone of human existence!), pregnancy is more complicated than you might think. The existence of the fetus is only the start; there are also hormonal shifts, metabolic changes, and hugely complex varieties of signaling by which the body communicates to its various systems that it's Building Something. That complexity does mean, though, that it's possible for conditions to exist which mimic the symptoms of pregnancy without there actually being a fetus in the mix. If the signaling goes wrong in some way, or if another disease interferes with the ways in which the female body deals with its reproductive system, all signs will point to FETUS — even though there's no fetus in sight.
I'm not including syndromes that just involve the suppression of the menstrual cycle, even though we've all had that panicked moment in a bathroom when we realize our period's a bit late. (The female body can essentially act like a giant troll at times while it's sorting out its menstrual cycle.) Many innocuous things can cause periods to stop or be late, from stress to weight loss or gain to shifting around your contraception. What we're talking about here is more comprehensive: conditions that ape the symptoms of pregnancy, from the swollen belly to heart palpitations, enlarged breasts and tiredness. The only way to be absolutely certain that pregnancy is the cause of your symptoms is a comprehensive examination by your doctor. As you'll discover, home pregnancy kits aren't exactly reliable on this one.
1. Ovarian Cancer
The presence of tumors on your ovaries have the potential to create multiple symptoms that mimic pregnancy: sufferers speaking to Marie Claire mentioned everything from missed periods and swollen abdomens to an increased need to urinate. The reasoning is fairly simple (though often traumatic for those experiencing it): the ovaries are responsible both for the production of eggs and for the release of progesterone and estrogen; tumors directly within or on them will interfere with these functions, creating hormone imbalances that can lead to menstrual disturbances and other symptoms that could be mistaken for pregnancy.
One of the ways in which ovarian cancer can cause severe confusion in diagnosis is the possibility of causing "positive" pregnancy tests. Here's how that works: in rare cases, ovarian and bladder cancers can cause a rise in the hormone human chorionic gonadotropin, or HCG, which is what's detected in home pregnancy urine tests. But there's a myth that pregnancy tests can actually be used to test for ovarian cancer itself, which the cancer organisation Ovarian Cancer Action thoroughly debunks; the phenomenon is rare, and the only guaranteed way of diagnosing ovarian cancer is a blood test and an ultrasound.
2. Thyroid Disorders
The thyroid gland controls the body's metabolism, and when it's disturbed due to a thyroid disorders (hyperthyroidism, where it's over-active, and hypothyroidism, where it's sluggish), it can produce bodily symptoms that resemble pregnancy. An overactive thyroid is a more common culprit; the body tends to accelerate its metabolic processes during pregnancy, in a very similar way to the up-tick in metabolism caused by hyperthyroidism. The clinical medical guide Women's Health states, "many of the classic signs of hyperthyroidism resemble the physiologic adjustments of normal pregnancy, such as emotional lability, heat intolerance, palpitations, and tachycardia".
But though hypothyroidism leads to different symptoms, they can also be mistaken for pregnancy. Johns Hopkins Medicine explains that hypothyroidism's inactive thyroid can cause "fatigue, weight gain, and abnormal menstruation," plus trouble concentrating and changes in skin or hair. Medscape points out that this has a unique irony: hypothyroidism, in its severe form, can actually impair fertility, so sufferers may have all the conditions of pregnancy without actually having the end result.
In the catalogue of conditions that resemble pregnancy, this too has a strange place. It doesn't resemble pregnancy; rather, in the mind of the person experiencing it, it is pregnancy. Pseudocyesis, or false pregnancy, is the production of pregnancy-like symptoms in the bodies of people who aren't pregnant but fervently believe that they are. The technical definition is "a condition in which the patient has all signs and symptoms of pregnancy except for the confirmation of the presence of a fetus." It's alleged that historical queen Mary Tudor may have suffered from it.
"Those who suffer from the disorder," wrote the New York Times in a report on the disorder in 2006, "present a constellation of symptoms that mystify even seasoned practitioners. Not only do they fervently believe they are pregnant, but they also have bona fide symptoms to back up their claims, like cessation of menstruation, abdominal enlargement, nausea and vomiting, breast enlargement and food cravings." A 2012 look at the disease also mentions morning sickness and breast enlargement. How is it possible for a person to essentially trick themselves, and their bodies, into performing a pregnancy?
Pseudocyesis is primarily deemed a psychological disorder, though its mechanisms are not well-understood; it seems that some psychological cues can trick numerous gland and hormonal cues into emulating pregnancy in a woman. It's now far rarer than it used to be, possibly because of greater education about pregnancy itself, and doctors have suggested that strong societal pressure and possibly some kind of vulnerability in the pituitary gland can both contribute to pseudocyesis's occurrence. There's also been some brain science done on the nervous systems of women with pseudocyesis that suggests some interesting differences; but fundamentally, as one of the rarest disorders in psychology, there's not a big sample size to test.
The Bottom Line
All of these conditions are rare, or at least rarer than a healthy pregnancy. But they do make something clear: you shouldn't completely count on a pregnancy being real until you've had a full examination with a doctor, as there's a slim chance it may be something else.
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