This is no easy month for Supreme Court Justice Harry Blackmun. The tenth anniversary of the Jan. 22, 1973, decisions that struck down abortion laws in 50 states is a moment for looking back at the language Blackmun wrote for the court.

Instead of an increase in stature as the years pass--as is true of great Supreme Court opinions--the test of time, and only 10 years at that, has shown Blackmun's thinking to be fuzzy then and fuzzier now.

He wrote that the word "person," as used in the 14th amendment, "does not include the unborn." He dismissed as merely "a theory of life" the idea held by the losing side that the rights of the pregnant woman are not the only rights involved. Blackmun did speak of "potential life" at a later stage of pregnancy, in the third trimester.

Advances in fetology--the health care of the preborn--have become so common in 10 years that Blackmun's thinking is even medically obsolete. Physicians, not only ethicians, have said through their efforts to save and protect fetal life that the preborn have rights.

Blackmun did refer to the losing side's interest in protecting "potential life"--but only after viability, which in his view was usually after seven months. Should a woman want an abortion at that time, when non-persons can be felt making non- movements in the womb, the ruling dictates that states may proscribe it only for reasons of maternal health or life.

Blackmun's discussion of health was broad, to the point of being meaningless: it includes "all factors--physical, emotional, psychological, familial, and the woman's age --relevant to the well-being of the patient." In a crucial line, Blackmun added that "this allows the attending physician the room he needs to make his best medical judgment."

It provided so much room that fetal life after viability was not protected at all. The ruling took the hassle out of doctor-shopping, the pre-1973 practice in which two physicians were needed in many states to sign off for a "therapeutic" abortion. The court eased this into a mere "well-being" abortion.

In his decisions, Blackmun placed strong jurisprudential faith in the expertise of doctors. In "this most sensitive and difficult question," the "professional judgment" of the physician is needed because abortion is a "medical decision."

Some doctors, in fact, have been uneasy recipients of the excessive faith the court placed in their professionalism. Those who specialized in medical ethics had different ideas about viability, the essence of the debate. Dr. Andre Hellegers wrote that "in induced abortion it's the physician's action which causes the lack of viability. It seems like an aberration that the very act which makes the fetus non-viable should find its justification for some in the fact that the resulting fetus is precisely non-viable. The fact that an adult who cannot swim is not viable hardly seems a sufficient justification for throwing him overboard and thus making him non-viable."

The language of the court, shying from meaningful discussion of the morality and ethics of destroying fetal life, kept the issue on the level of professional health care. That was perfect for many doctors. The pricing structure of abortions suggests that, with 1.5 million performed annually, what's good for the "well-being of the patient" can be even better for the financial well-being of doctors toiling in the abortion industry.

Dr. Bernard Nathanson, a New York obstetrician who presided over 60,000 abortions until he had second thoughts and left the trade in the mid-1970s, commented about the pay system at his clinic: "Doctors were earning more than $1,000 on an eight- hour shift, with two abortions an hour and, in some cases, three. Some worked two shifts a day and doubled their income."

According to a new survey by the Alan Guttmacher Institute, the average clinic fee for a first trimester abortion is $190. For the second trimester, it is $358. In hospitals, the charge is $735 and $740. Sixty-nine percent of the clinics, with clinics doing nearly three-fourths of the abortions, were run for profit. Nearly 40 percent were owned by corporations.

The court decision and the business boom are separate issues. But why did Blackmum advance the doctor-knows-best line? If the past 10 years have shown anything, it is that doctors of conscience have been the first to confess that in questions of taking fetal life they don't know best.

Which is why abortion cases keep coming back to the Supreme Court. Doctors want some guidance laced with substance, which they didn't get in 1973.