Christian objection to abortion goes way, way back.

The Didache, an early Christian treatise from the first century, explicitly bans abortion, though it doesn't say why.

In 197, Tertullian wrote "Since Murder is altogether forbidden for us, it is not permissible even to destroy what has been conceived in the womb, while blood is still being gathered into a human. To prevent birth is the hastening of murder, and it does not matter whether someone takes away a soul that is born or destroys one that is nascent. What will be a human is human; the whole fruit is already in the seed" Apologeticum 9.8. So here we see the argument of the soul beginning at conception.

Justinian (527-565 CE) had this to say: a woman who procured an abortion should be punished because "it might appear scandalous that she should be able to deprive her husband of children without being punished." (Digest 47.11) So for him it was more about controlling women than about the life of the fetus.

So, although objection to abortion probably wasn't universal among early Christians (indeed, few things were), it's definitely been a strong current in Christian thought since the beginning.

Abortion became a political issue in the US in the early-mid 19th century when a handful of laws were put into place in different states, though rarely were people prosecuted. Abortion was perfectly (or practically) legal in most places until the "quickening"- the time when a fetus' movement is first felt- until the late 19th century.

The Catholic Church began to condemn abortion around the same time that physicians did- the mid-late 19th century. Advances in medical science pushed the definition of "life" back from the quickening to conception. Other branches of Christianity became anti-abortion at different times.

The real ramp up in hysteria around pregnancy came during the rise of the eugenics era. There was a fear that the "wrong" people were getting abortions (ie married, middle class, anglo-women) and were committing "race suicide."

You might want to check out "When Abortion Was a Crime: Women, Medicine, and Law in the United States, 1867-1973" by Leslie Reagan.