A hydatidiform mole is a mass developed within the uterus of a woman from the surface layer of the placenta. It is suspected during symptoms of pregnancy, but much more alarming: significant genital blood loss, nausea, or vomiting. The amount of HCG, pregnancy hormone, found at unusually high levels and an ultrasound will confirm the diagnosis. The hydatidiform mole must be removed from the uterus by suction. This is not to be confused with the mole which is a unit of measurement corresponding to molecular weight. It corresponds to the mass of 6.022 multiplied by 10 to the power of 23 (1 with 23 zeros behind it) molecules of a substance. It is used in medicine in certain biological measurements such as the amount of serum creatinine, which is expressed as millimoles per liter of blood.