Thanks to a federal judge in New York, millions of American girls have got at least a temporary reprieve from federal intervention in their sex lives.

By granting a preliminary injunction against a requirement that family-planning clinics inform the parents of teen-agers who obtain birth-control devices, U.S. District Court Judge Henry F. Werker has struck a resounding blow for fair play, as well as common sense. The regulation drawn up by the Department of Health and Human Services applies only to prescription birth control, which is used exclusively by young women. It may take two to tango, but only one party would have had to face the music at home.

While backers of the regulation talked about the benefits of parental involvement in teen-agers' decisions about sex, the judge came down on the side of its opponents, who cited surveys showing that 25 percent of young people attending clinics would stop going if their parents were notified. The judge said the regulation would lead to increased teen-age pregnancies, the opposite of what Congress intended.

The cost of teen-age pregnancy is enormous. Some 1.2 million teen-agers get pregnant each year, three-quarters of them unintentionally. Dr. Carol Gregg of the Center for Population Options cites Urban Institute data showing that 75 percent of the teen-agers who give birth will eventually require some form of public subsidy. The U.S. spends $8.6 billion a year to support women who became mothers as teen-agers and their children.

Between 80 and 90 percent of the teen-age girls who become pregnant drop out of school and generally they don't go back. Teen-age fathers are 40 percent less likely to graduate from high school.

The Alan Guttmacher Institute has developed data that consistently shows that teen-agers are poorly informed about contraception, that most don't use any until long after they become sexually active, and that if they did use contraception reliably, the birthrates could be cut by 40 percent or more.

There is, in other words, a crying need for a tremendous public information and education campaign aimed at the 2 million sexually active teen-agers who are not getting contraceptives from clinics or physicians.

The Center for Population Options is currently running a project in Durham, N.C., designed to get teen-agers in vocational programs to think about the impact of pregnancy on future employment. "One of the reasons we focus on economic outcome, is teens don't seem to be deterred by the health consequences of teen-age pregnancy," says Gregg. "What seems to be important is their ability to support themselves, and their babies . . . By helping young women and young men to focus on what they want from their lives, we might be able to get across the idea that they must postpone pregnancy until they are on the way to achieving their goals."

HHS has, in the past, joined with private groups to run a national campaign alerting teen-agers to the dangers of smoking. There is no reason it could not join with family-planning providers to mount a massive information campaign using television, radio spots and whatever else is appropriate to warn teen-agers about the consequences of pregnancy. Today's teen-ager, who comes complete with skis, portable radio and other consumer goods, is likely to at least listen to the bleak economic forecast.

Public information spots could also inform teen-agers of the higher health risks that exist for young mothers and their children. And, says Gregg, they "need a lot more education" about the dangers of herpes, and gonorrhea, which has left tens of thousands of young women sterile. And it is through an educational campaign that HHS can urge parents to teach their children to act responsibly about sex, just as they are expected to make sure their children act responsibly about driving.

HHS' initial assault on teen-age pregnancy was strangled in contradictions, not the least of which was a deregulating administration regulating the most intimate of matters. Nevertheless, the skirmish has drawn attention to the role of parents in this aspect of their children's lives and has focused national attention on the problem of teen-age pregnancy.

The administration has the opportunity now to capitalize on this new public awareness and to mount a public information offensive that properly handled would enjoy widespread support, and might do more good than parental notification rules ever could.