Abortion is defined as the termination of pregnancy
Pregnancy (mammals)
In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus; and ends once it leaves the uterus.-Fertilization and implantation:A...

 by the removal or expulsion from the uterus of a fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 or embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 prior to viability. An abortion can occur spontaneously, in which case it is usually called a miscarriage
Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...

, or it can be purposely induced. The term abortion most commonly refers to the induced abortion of a human pregnancy.

Abortion, when induced in the developed world
Developed country
A developed country is a country that has a high level of development according to some criteria. Which criteria, and which countries are classified as being developed, is a contentious issue...

 in accordance with local law
Abortion law
Abortion law is legislation and common law which pertains to the provision of abortion. Abortion has been a controversial subject in many societies through history because of the moral, ethical, practical, and political power issues that surround it. It has been banned frequently and otherwise...

, is among the safest procedures in medicine.

Abolition of a woman's right to abortion, when and if she wants it, amounts to compulsory maternity: a form of rape by the State.

Edward Abbey, One Life at a Time, Please (1988)

The poor InfanticideInfanticide_in_history|expose their children, the rich kill the fruit of their own bodies in the womb, lest their property be divided up, and they destroy their own children in the womb with murderous poisons, and before life has been passed on, it is annihilated.

St. Ambrose|St. Ambrose, circa 370

Every person has the right to have his life respected. This right shall be protected by law and, in general, from the moment of conception. No one shall be arbitrarily deprived of his life.

wikipedia:American Convention on Human Rights|American Convention on Human Rights, Article 4, 1969, ratified by 25 member-states of the Organization of American States

Concerning women who commit fornication, and destroy that which they have conceived, or who are employed in making drugs for abortion, a former decree excluded them until the hour of death, and to this some have assented. Nevertheless, being desirous to use somewhat greater lenity, we have ordained that they fulfill ten years [of penance], according to the prescribed degrees.

Synod_of_Ancyra|Synod of Ancyra canon XXI, circa 314

Supporters of [the Human Life Amendment] are often eloquent in their defense of the fertilized egg but are seldom willing to aid the woman whose body nourishes it.

Carole Anderson and Lee Campbell with Mary Anne Cohen, reprinted in Our Bodies, Ourselves|The New Our Bodies, Ourselves, Boston Women's Health Book Collective (1984)