This paper examines the issue of medical uncertainty in Chinese gynecology by analyzing how classical medicine defined and explained different forms of false pregnancy. Besides recognizing that false pregnancies could mimic true ones, Chinese gynecology also recognized that true fetuses could deviate from the normal course of gestation and thus mimic false pregnancies. Therefore, the paper argues that the perceived difficulty of distinguishing between true and false pregnancies was intimately linked to the belief that female reproductive energies were easily subverted by external pathogens and internal imbalances. Special attention is given to the syndrome known as Ghost Fetus, which was originally explained as the product of human-ghost intercourse but later understood primarily as the result of excessive female emotion. During the Qing, furthermore, discussions of Ghost Fetus and other forms of false pregnancy frequently merged into discussions of female depletion and menstrual irregularity. The paper concludes that these changes in the definition of Ghost Fetus are part of a larger change in gender norms during the Ming-Qing that increasingly focused on female emotionality and physical debility.