Abortion in the United States , and abortion-related issues , are the subject of intense public and political debate and discussion in the United States . Various anti-abortion laws have been on every state statute book since at least 1900. Abortion was prohibited in 30 states and legal under certain circumstances (such as pregnancies resulting from rape or incest) in 20 states. The Supreme Court 1973 decision Roe v. Wade invalidated all of these laws, and set guidelines for the availability of abortion.
Roe established that the abortion right "must be considered against important state interests in regulation." [ 1 ] Roe established a "trimester" threshold of state interest in the life of the fetus corresponding to its increasing "viability" (likelihood of survival outside the uterus) over the course of a pregnancy, such that states were prohibited from banning abortion early in pregnancy but allowed to impose increasing restrictions or outright bans later in pregnancy.