You are wrong. The Church up to St. Augustine, starting with +Barnanbas and +Clement, all the way through the Council of Elvira, the Church held that nothing justified abortion.
St. Augustine (4th century), in his On Exodus (21, 80) changed all that (and then some). He embraced pagan Aristotelian theory known as "delayed ensoulment" which basically states that human soul cannot abide in an unformed body.
Thus a fetus destroyed before it begins to "look" human was not considered human because it didn't have human soul according to that theory, and therefore destroying a fetus before 40 days of gestation (90 days for females) was not considered murder.
That this is what the Church believed in the 5th century is made crystal clear by St. Jerome says in his Epistle [121, 4]
"The seed gradually takes shape in the uterus, and it [i.e. abortion] does not count as killing until the individual elements have acquired their external appearance and their limbs
According to the early 8th century penitential of the Church in England, oral sex was punishable by years to a lifetime of penance; aboriton only 120 days!
Obviously the Church did not consider abortion to be on the par with "alternative" sex practices.
At the end of the 9th century, Pope Stephen V in his letter to the Archbishop of Mainz sows that abortion was not equal to infanticide:
"If he who destroys what is conceived in the womb by abortion is a murderer, how much more is he unable to excuse himself of murder who kills a child even one day old."
Pope Innocent III (late 12th century, early 13th century) ruled that a Carthusian monk who arranged for his lover to have an abortion ruled that he wa snot guilty of murder if the fetus was not animated.
He taught that the fetus is animated when the woman begins to feel its movement (quickening). After that point abortion was equal to murder (homicide).
St. Thomas Aquinas, also 13th century, shared this view.
In the 15th century, Pope Sixtus V basically prohibited abortion at any stage. This was revoked by Pope Gregory XIV (5th century) who re-set the "timer" to 116 days (vs 40/90 of Augustinian time)
By the 17th century, with advancing medical knowledge, the Church developed what is known as the "simultaneous animation." It was a Franciscan monk Hieronymus Florentinius who stated that all aborted fetuses must be baptized, but this was not the Church teaching.
It was not until Pope Pius IX that any definition of "animation" was dropped in 1869, but abortion per se was still not outlawed by the Church .
It was Pope Leo XIII who prohibited any form of abortion that caused death to the fetus. He did that in 1886.
Nevertheless, with Immaculate Conception as a dogma and the official teaching of the Church, there is no room for any Catholic to appeal to historical precedence, which was obviously based on the false (pagan) belief in various stages of animation.
Respect for Unborn Human Life: The Church’s Constant Teaching (PDF)
The Catechism of the Catholic Church states: “Since the first century the Church has affirmed the moral evil of every procured abortion. This teaching has not changed and remains unchangeable. Direct abortion, that is to say, abortion willed either as an end or a means, is gravely contrary to the moral law” (No. 2271).
In response to those who say this teaching has changed or is of recent origin, here are the facts:
- From earliest times, Christians sharply distinguished themselves from surrounding pagan cultures by rejecting abortion and infanticide. The earliest widely used documents of Christian teaching and practice after the New Testament in the 1st and 2nd centuries, the Didache (Teaching of the Twelve Apostles) and Letter of Barnabas, condemned both practices, as did early regional and particular Church councils.
- To be sure, knowledge of human embryology was very limited until recent times. Many Christian thinkers accepted the biological theories of their time, based on the writings of Aristotle (4th century BC) and other philosophers. Aristotle assumed a process was needed over time to turn the matter from a woman’s womb into a being that could receive a specifically human form or soul. The active formative power for this process was thought to come entirely from the man – the existence of the human ovum (egg), like so much of basic biology, was unknown.
- However, such mistaken biological theories never changed the Church’s common conviction that abortion is gravely wrong at every stage. At the very least, early abortion was seen as attacking a being with a human destiny, being prepared by God to receive an immortal soul (cf. Jeremiah 1:5: “Before I formed you in the womb, I knew you”).
- In the 5th century AD this rejection of abortion at every stage was affirmed by the great bishop-theologian St. Augustine. He knew of theories about the human soul not being present until some weeks into pregnancy. Because he used the Greek Septuagint translation of the Old Testament, he also thought the ancient Israelites had imposed a more severe penalty for accidentally causing a miscarriage if the fetus was “fully formed” (Exodus 21: 22-23), language not found in any known Hebrew version of this passage. But he also held that human knowledge of biology was very limited, and he wisely warned against misusing such theories to risk committing homicide. He added that God has the power to make up all human deficiencies or lack of development in the Resurrection, so we cannot assume that the earliest aborted children will be excluded from enjoying eternal life with God.
- In the 13th century, St. Thomas Aquinas made extensive use of Aristotle’s thought, including his theory that the rational human soul is not present in the first few weeks of pregnancy. But he also rejected abortion as gravely wrong at every stage, observing that it is a sin “against nature” to reject God’s gift of a new life.
- During these centuries, theories derived from Aristotle and others influenced the grading of penalties for abortion in Church law. Some canonical penalties were more severe for a direct abortion after the stage when the human soul was thought to be present. However, abortion at all stages continued to be seen as a grave moral evil.
- From the 13th to 19th centuries, some theologians speculated about rare and difficult cases where they thought an abortion before “formation” or “ensoulment” might be morally justified. But these theories were discussed and then always rejected, as the Church refined and reaffirmed its understanding of abortion as an intrinsically evil act that can never be morally right.
- In 1827, with the discovery of the human ovum, the mistaken biology of Aristotle was discredited. Scientists increasingly understood that the union of sperm and egg at conception produces a new living being that is distinct from both mother and father. Modern genetics demonstrated that this individual is, at the outset, distinctively human, with the inherent and active potential to mature into a human fetus, infant, child and adult. From 1869 onward the obsolete distinction between the “ensouled” and “unensouled” fetus was permanently removed from canon law on abortion.
- Secular laws against abortion were being reformed at the same time and in the same way, based on secular medical experts’ realization that “no other doctrine appears to be consonant with reason or physiology but that which admits the embryo to possess vitality from the very moment of conception” (American Medical Association, Report on Criminal Abortion, 1871).
- Thus modern science has not changed the Church’s constant teaching against abortion, but has underscored how important and reasonable it is, by confirming that the life of each individual of the human species begins with the earliest embryo.
- Given the scientific fact that a human life begins at conception, the only moral norm needed to understand the Church’s opposition to abortion is the principle that each and every human life has inherent dignity, and thus must be treated with the respect due to a human person. This is the foundation for the Church’s social doctrine, including its teachings on war, the use of capital punishment, euthanasia, health care, poverty and immigration. Conversely, to claim that some live human beings do not deserve respect or should not be treated as “persons” (based on changeable factors such as age, condition, location, or lack of mental or physical abilities) is to deny the very idea of inherent human rights. Such a claim undermines respect for the lives of many vulnerable people before and after birth.
For more information: Congregation for the Doctrine of the Faith, Declaration on Procured Abortion (1974), nos. 6-7; John R. Connery, S.J., Abortion: The Development of the Roman Catholic Perspective (1977); Germain Grisez, Abortion: The Myths, the Realities, and the Arguments (1970), Chapter IV; U.S. Conference of Catholic Bishops, On Embryonic Stem Cell Research (2008); Pope John Paul II, Evangelium Vitae (1995), nos. 61-2.