I really don't like the abolitionist comparison.
No slave owner was forced to choose between owning a slave and going through a year long physical and emotional hardship. The loss of cheap labor does not equate.
Also, I do lean toward the idea that many (not all) pro-life advocates are "enslaving women" for this reason:
Power in societies are controlled through population. This is why the Catholic Church is anti-birth control and anti homosexuality. The more babies you have, the more powerful the people in charge become. (Yes, this is conjecture, but I think we can agree with the reasoning here.) And the catholic church is a huge force behind the pro-life movement. And while individual catholics might not be trying to increase the population with anti-abortion laws or abstinance-centered sex education, their leaders sure are.
To me, it's either "enslaving the fetus" to the medical choices of the mother or "enslaving the woman" to the medical choices of a zygote. And the woman comes first. (edited to add: at least to the point where the fetus stops being parasitic)