"The Equal Protection Clause of the Fourteenth Amendment requires the states to “exercise their powers so as not to discriminate between their inhabitants except upon some reasonable differentiation fairly related to the object of regulations.” The challenged statute operates to deny equal protection to women with compelling reasons for receiving therapeutic abortion, concurred in by their physicians, but whose physicians cannot advance as “medical advice” that the abortion is necessary to “save” their lives. Women so excluded are those who would suffer a serious impairment of physical or mental health from carrying a pregnancy to term, those whose pregnancies are the result of rape or incest, those whose fetuses will, with high medical certainty, be born with gravely disabling physical or mental defects, and those who are financially unable or emotionally incapable of supporting a child, or of adding another child to a family whose limited resources are already strained by their devotion to raising children in being. [T]he fundamental interest involved in the case of each of the excluded classes of women is as deserving of constitutional protection as the “saving” (whatever it may mean) of the mother’s life. Compelling a woman to give birth to a child which is the product of rape or incest, or which will be born deformed, or whose birth will damage the woman’s own health or capacity to be a mother to the child or to her existing family, may be as unbearable to the woman as a vague threat to her life itself. That compulsion also puts her physician in the ethically questionable position of having to decide just how much injury he must allow her to bear, despite his obvious ability to prevent that injury, before he can confidently say to the prosecutor that he ultimately acted to save her life."