A Phantom pregnancy is a non-medical term of Pseudocyesis, which is a disorder that affects a very small number of women of child bearing age, and refers to a false sensation of being pregnant in a woman who is not. In mammals pseudocyesis is called pseudopregnancy; however, in humans, it is termed Pseudocyesis.
In clinical Pseudocyesis, the female reproductive system will mimic that of a normal pregnant woman, and many endocrine changes will occur.
It is still not determined what causes Pseudocyesis (or Phantom Pregnancy) but is has been associated with endocrine disorder and psychological disorders; however it has not been identified which area triggers the other.
It is however, recognised as a definite disorder that does occur in a small number of woman.