How did Christians respond to abortion in the early Church? I think that the churches (all Christians, Catholics, Protestants, Greek Orthodox and others) should be involved in the fight against legalized abortion. I am looking to the history of the Church to see what forms of abortion occurred (e.g., abandonment/exposure), and how the early Church Christians responded, and the prevailing doctrines on abortion or its equivalent.
There were church commandments against it, and from the earliest times.

The Didache, i.e. the earliest Christian catechetical document (and contemporaneous with the Gospels, probably earlier than A.D. 70) says "οὐ φονεύσεις τ́κνον ἐν φθορᾷ" (you shall not murder an infant with abortion) and "οὐδὲ γεννηθὲν ἀποκτενεῖς" (nor slay the begotten). So both abortion pre-birth and the monstrous ancient (and regrettably, and shockingly, current) practice of awaying with unwanted and undesirable babies is here condemned.

Athenagoras, also a very early Christian, writes in his A Plea for Christians (a work against calumnies against the Christian faith by pagans, to the Roman Emperor), cap. 35:


  And when we [Christians] say that those women who use drugs to bring on abortion commit murder, and will have to give an account to God for the abortion, on what principle should we commit murder?


He wrote about A.D. 177.

Tertullian, writing in 197 (Apology, cap. 9):


  In our case [Christians'], murder being once for all forbidden, we may not destroy even the fœtus in the womb, while as yet the human being derives blood from other parts of the body for its sustenance. To hinder a birth is merely a speedier man-killing; nor does it matter whether you take away a life that is born, or destroy one that is coming to the birth. That is a man which is going to be one; you have the fruit already in its seed.


This sentiment, attitude, doctrine, is never taken back or rejected by any later Christians, so to cite more would be rather superfluous. That is to say, all abortion is considered murdering that infant.