[elwoodblues]

That's kind of what Roe v. Wade did. Roe v. Wade set forth three different standards depending on the stage of fetal development --- basically the argument was that the state's interest increased as the fetus became more viable. The standard was (roughly):

First Trimester: The state cannot restrict the right to an abortion

Second Trimester: The state may regulate abortion to the extent that the regulation deals with the health/well-being of the mother

Third Trimester (fetal viability): The state may regulate/ban abortions except in the cases where the life/health of the other are at risk