Would a compulsory abortion law be constitutional?

[🐒Gods of Prosperity🔱🐲💸]

No.  It's clearly against the traditions and understanding of natural law which undergird the Constitutional order. If there would ever a place for a Ninth Amendment decision this would be it.  Additionally:

If it's done in a discriminatory manner toward either parent or child, it's an Equal Protection violation.
If it's done in response to a crime, it's a No Cruel and Unusual Punishment violation.
If it's not done in response to a crime, it's a Due Process violation.
In cases where it's against someone's religious or similar moral convictions, it's becomes a Free Exercise issue.

Could be considered a legitimate penumbra (if you believe in those) more than a supposed right to an abortion ever was.

Also there's an decent argument for considering a fetus to be a person under the 14th amendment. It's one thing for a state to be agnostic or nuanced on this question, it's another to declare the unborn has no rights. There may be various limits and competing interests and prudential considerations which prevent abortion to be generally treated the same as murder, but at the very least the state should be prohibited from acting with intent to harm fetal life.