Anyway, I find people's thinking around the morals of abortion to be quite fluid . The termination rate of pregnancies with chromosomal abnormalities far exceeds the percentage of people who identify as "pro choice" and cannot be explained simply by pro-choice people being more prone to fetuses with such conditions.
There are plenty of pro-choice arguments, but this is not a very good one.
Coercion is often justifiably used when lives are at stake. For example, the government might "force" sick people in a quarantine given an epidemic outbreak. What you want to show is that the fetus is not a person and, therefore, doesn't have the same rights as the mother. This is difficult, but not impossible -- although there are some concessions that need to be made along the way.