1. Expulsion from the uterus of an embryo or fetus prior to the stage of viability at about 20 weeks of gestation (fetus weighs less than 500 g). A distinction is made between abortion and premature birth: premature infants are those born after the stage of viability but prior to 37 weeks. Abortion may be either spontaneous (occurring from natural causes) or induced (artificial or therapeutic).
2. The product of such nonviable birth.
3. The arrest of any action or process before its normal completion.
accidental abortion
ampullar abortion
complete abortion
criminal abortion
elective abortion
enzootic abortion of ewes
epizootic bovine abortion
equine virus abortion
foothill abortion
habitual abortion
illegal abortion
imminent abortion
incipient abortion
incomplete abortion
induced abortion
inevitable abortion
infected abortion
menstrual extraction abortion
missed abortion
septic abortion
spontaneous abortion
therapeutic abortion
threatened abortion
tubal abortion
vibrionic abortion