APPARENTLY IT WILL be a couple of weeks before this year's floor fight over the Hyde Amendment takes place in the House. The Hyde Amendment is that brief but consequential provision drafted by Rep. Henry Hyde (R-Ill.) and appended last year and this to the Labor-HEW appropriations bill. It would prohibit the use of Medicaid money to pay for abortions unless "the life of the mother would be endangered if the fetus were carried to term." Although the amendment was enacted into law last year, a federal court in New York enjoined its use, so the prohibition was never enforced and has been in legal limbo ever since.

We don't think the Hyde Amendment looks any better this year than it did last. It is a bad legislation - badsocial policy and bad constitutional law. Its effect would be to deny poor women a medical service available to those who are better off, one that also has been pronounced legal - except in certain circumstances - by the Supreme Court. But a few things are different this year. One is that Jimmy Carter is President and Joseph A. Califano Jr. is Secretary of HEW and both have, unfortunately, committed themselves to the wrong side of the argument; both have pledged to oppose the use of federal funds to pay for abortions, whether under Medicaid or under the terms of a prospective new national health insurance plan.

Although this issue, in all probability, is ultimately going to be resolved by the federal courts, the immediately arena is Congress, and the strong feelings of the President and Mr. Califano could well have an impact on the legislative outcome. For that reason it is important that the opponents of the Hyde Amendment argue their case humanely and well, and it seems to us that one argument being emphasized this year does not fit that description. We refer to the economic rationale, the claim that poor women should be granted state-subsidized abortions because, otherwise, society will have to assume the extremely high costs of raising and caring for the children they bear.

This is a terrible argument. Its implications are monstrous. Sen. Jesse Helms (R-N.C.), who supports the Hyde Amendment and with whom we believe we have a virtually unblemished record of disagreement to date, did nonetheless, in our judgment, score the relevant point last year when the economic argument was made in debate. "In other words," he replied, "what we are saying is it is cheaper to the state to kill the unborn children of the poor than it is to let them be born."

Yes, that is a crude and strained way of saying it, but that is the implication of the argument. All of the other reasons given for fighting the Hyde Amendment can stand on their own: They deal with questions of equity, safety, health, due process. But the economic argument, by itself, cannot. We are aware of the irony here, namely, that the economic argument is likely to be quite persuasive with members of Congress who are insensitive to the better reasons for opposing Mr. Hyde. Even so, we think the opponents of the amendment, among whom we count ourselves, should leave off telling folks how much better a bargain abortion is than birth from the taxpayer's point of view. The issue isn't bargains - it's equal protection of the law.