The practice of human abortion destroys the God-endowed, natural unity of the mother and the child, in the most violent way possible.
But it also destroys the unity of the parents, and the unity of the family, and the unity of the community, and the unity of the nation. which means that it destroys the first stated purpose of the U.S. Constitution, the supreme law of our land.
Which, of course, means that it always has been, and is, illegal. Don't ever let anyone tell you otherwise.
By the way, abortion destroys all of the other clauses of the stated purposes of our Constitution as well.
"We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America."
-- The Preamble, or Statement of Purpose, of the United States Constitution