Miscarriage or spontaneous abortion is the natural or spontaneous en of a pregnancy at a stage where the prenate is incapable of surviving, generally defined in humans at a gestation of prior to 20 weeks. Miscarriage is the most common complication of early pregnancy. The medical term "spontaneous abortion" is used in reference to miscarriages because the medical term "abortion" refers to any terminated pregnancy, deliberately induced or spontaneous, although in common parlance it refers specifically to active termination of pregnancy.