According to WebMD, a woman is able to experience pregnancy symptoms without actually being pregnant; this is termed "pseudocyesis." Doctors have a theory that psychological factors trick the body into thinking its pregnant when it is really not.
WebMD says that pseudocyesis is caused by a woman having a strong desire to become pregnant for whatever reason, so her body makes her believe she really is. The woman's brain misinterprets signals and releases hormones similar to those of actual pregnancy.
The New York Times states that symptoms of pseudocyesis, or false pregnancy, include the absence of a menstrual period, food cravings, increased abdominal size, vomiting, nausea, food cravings and breast enlargement. The difference between between pseudocyesis and pregnancy is the absence of a fetal heart rate, a fetal image on a sonogram and the delivery of a baby, according to the New York Times.
While some cases of false or phantom pregnancy last a week or two, Baby Center says that many women have these symptoms for months. The condition is very rare; it is seen only in one to six out of every 22,000 live births, according to WebMD. Baby Center indicates that it is difficult for some women to hear the news that they are not actually pregnant, so they have a phantom pregnancy.