History does not support the Anti-abortion position
Circa 380: The Apostolic Constitutions allowed abortion if it was done early enough in pregnancy. But it condemned abortion if the fetus was of human shape and contained a soul.
St. Augustine (354-430) accepted the Aristotelian Greek Pagan concept of "delayed ensoulment". He wrote that a human soul cannot live in an unformed body. 3 Thus, early in pregnancy, an abortion is not murder because no soul is destroyed (or, more accurately, only a vegetable or animal soul is terminated).
Pope Innocent III (1161-1216): He determined that a monk who had arranged for his lover to have an abortion was not guilty of murder if the fetus was not "animated" at the time. Early in the 13th century, he stated that the soul enters the body of the fetus at the time of "quickening" - when the woman first feels movement of the fetus. Before that time, abortion was a less serious sin, because it terminated only potential human person, not an actual human person.
St. Thomas Aquinas (1225-1274): St. Thomas thought that the soul did not come to the fetus ('ensoulment') until sometime after conception. In fact, he considered abortion gravely sinful, teaching that it was a grave sin against the natural law to kill the fetus at any stage and a graver sin of homicide to do so after ensoulment.
Pope Sixtus V (1588) issued a Papal bull "Effraenatam" which threatened those who carried out abortions at any stage of gestation with excommunication and the death penalty.
Pope Gregory XIV (1591) revoked the previous Papal bull and reinstated the "quickening" test, which he determined happened 116 days into pregnancy (16½ weeks).