Recent case studies of pseudocyesis, or false pregnancy, as well as studies of similar conditions in animals, suggest that hormones and psychology might contribute to the condition, the New York Times reports.
According to the Times, women who experience pseudocyesis -- which occurs one to six times per 22,000 births -- have many symptoms of pregnancy, including lack of menstrual periods, abdominal enlargement, nausea and vomiting, and breast enlargement.
In addition, some women experiencing pseudocyesis have positive results on pregnancy tests, according to Paul Paulman, a family practitioner at the University of Nebraska Medical Center.
The condition has been treated largely by psychiatrists, who have many theories as to why the condition occurs, including that it "occurs in patients who desperately want to become pregnant or who have a strong desire to be involved in a family member's pregnancy," the Times reports.
Although large-scale studies to establish a hormonal profile of pseudocyesis patients have not been preformed, individual case studies have indicated the women had increased levels of the hormones estrogen and prolactin, which cause abdominal swelling and breast milk excretion, according to the Times.
Mary Erskine, a Boston University biologist who studies the neurology of reproductive systems, said emotional states, such as anxiety, could induce abnormal hormone secretion, leading to physical and psychological effects.
"This is one of the classic examples in medicine of how the mind affects the rest of the body," Paulman said (Svoboda, New York Times, 12/5).