IT IS NOW OFFICIAL U.S. policy that if a woman or girl is raped, or is a victim of incest, and cannot affort private medical care, the federal government will pay for immediate treatment to prevent pregnancy. But if, as in so many cases, she is too traumatized or fearful to seek help before she knows she is pregnant, the government will not pay for an abortion. Unless she lives in a state that does provide such aid, the woman will be on her own.

That harsh policy is one consequence of the 1976 Hyde Amendment, which permits Medical payments for abortions only "where the life of the mother would be endangered if the fetus were carried to term." The law, which a federal judge allowed to take effect last week, runs out Sept. 30. One might think that, in setting next year's policy, the administration and Congress would at least show more compassion for those who become pregnant as a result of criminal assult. President Carter did say July 12 that a general ban of federally funded abortions should include an exception for victims of incest or rape. However, the administration seems to regard this as a minor and possibly abstract point, and apparently did not object when the House recently voted to extend the Hyde Amendment unchanged.

Even if Congress did provide for more human treatment for rape and incest victims, other problems would remain. For instance, the Hyde Amendment also bars federal payment for abortions when a fetus is deformed or when a woman is suffering from a chronic illness that childbirth could aggravate. And such examples point to the inherent defect in the categorical approach: No matter how exception-laden a general ban might be, it would inevitably deal arbitrarily with some situations involving real human distress.

In our view, that is the real trouble with such laws. They put the government in the business of making, on an impersonal basis, medical and moral judgements of the most intimate, consequential sort - and imposing those judgments on one class of citizens: those who happen to be poor. We think this is wrong. As a matter of public policy, we would prefer to see no statutory limitations on Medical payments for abortions at all. But Congress has not accepted that view. The best available alternative, in our judgment, is the Senate language, which would permit aid for abortions that are "medically necessary." That would at least leave the decisions to physicians and allow them the flexibility to make the best medical judgment in each individual case.