The world's first test tube baby turns 25 this month. You might know her name -- Louise Brown -- and that the pair of doctors responsible for her birth sounded vaguely like an old vaudeville team. You might know that those doctors, Steptoe and Edwards, were from Britain; if you were alive at the time, you might even remember that the city where they did their experiments, and where Louise was born, was Oldham.

But what you probably don't know, or don't remember, is how frightening it was to wait for that landmark birth. Most of those who were paying attention, from scientists to church officials to editorial writers, were sure that the world's first test tube baby would be abnormal: genetically deformed, less-than-human, monstrous, at the very least a freak of nature who would have to grow up with the eyes of the world charting its every move.

Amazingly, Louise was pink and perfect, normal in every way. When she arrived just before midnight on July 25, 1978, with 10 fingers, 10 toes and a lovely, lusty cry, she was graphic evidence that lab manipulations didn't have to harm the embryo. The age of assisted reproduction had begun.

The fears that preceded Louise's birth are similar to the fears today about other reproductive technologies. Some of the voices currently raised in opposition to the thorniest interventions -- cloning and designer babies in particular -- are the very same voices raised a generation ago in opposition to in vitro fertilization (IVF). And some of these voices are saying the very same things now that they were saying in the 1970s. But even if the players and the rhetoric are the same, the situation is not. We are, it seems, on the verge of learning the wrong lessons from the IVF experience, bending too far in the direction of over-regulating reproductive research because we have seen the unfortunate results of under-regulation.

Listen, for example, to Leon Kass, a bioethics professor at the University of Chicago whose voice has been part of this debate for 25 years. "More is at stake [with IVF research] than in ordinary biomedical research or in experimenting with human subjects at risk of bodily harm," Kass testified before the federal government's Ethics Advisory Board shortly after Louise Brown's birth. "At stake is the idea of the humanness of our human life and the meaning of our embodiment, our sexual being, and our relation to ancestors and descendants."

Kass is now President Bush's leading bioethics advisor, and when he talks about cloning he uses many of the same words he used in 1978. He sees moral ruin and calamity in the petri dishes where human embryos grow. Now as then, his concerns can be expressed in a simple shorthand: He worries about the so-called slippery slope.

The term implies a certain inevitability to scientific progress, an inability to put a stop to increasingly more loathsome applications of knowledge once we achieve that knowledge. If the slope of progress is indeed slippery, then any first step -- even if it is not objectionable when considered in isolation -- becomes objectionable because it could lead to some sort of abuse.

The slippery slope argument emerges often in scientific history, whenever a powerful new development might have dreadful ramifications. People talked about the slippery slope since the first artificial insemination was publicized in 1909, conjuring images of selective breeding and a race of illegitimate souls. They talked about it after the first heart transplant in 1967, after the first animal-to-human transplant in 1984, and, in 2002, after the first transplanted uterus. Early cases of assisted suicide stimulated talk about a slippery slope that would lead to wholesale killing of the aged or infirm; early attempts at amniocentesis begat fears about a slippery slope toward the elimination of fetuses that were imperfect in some way -- or that were simply the "wrong" sex.

To be sure, some of these first steps have led to brutal applications -- abortions of female fetuses in China and India, for example, and shameful experiences with eugenics around the world -- but fear of such horrors should not cause us to prohibit procedures that are in themselves innocuous, and that might easily lead to enhancement of our collective fate rather than to devastation.

If IVF was the first step down a slippery slope of its own, then it seems to have landed us in exactly the spot that Kass and others said it would. Earlier this month, two reports from the annual meeting of the European Society of Human Reproduction and Embryology made it seem that fun-with-embryos had gotten a little out of hand. An American scientist, Norbert Gleicher, announced that he and his colleagues had successfully inserted cells from a male embryo into an early-stage female embryo, creating a mixed-gender chimera that some journalists called a "she-male." Another team, from Israel and the Netherlands, described a trick that was even more bizarre: harvesting eggs from aborted fetuses and culturing them so they could be used in IVF, thereby creating a baby with a biological mother who had never been born.

No one would be talking about "she-male" embryos or fetal mothers if the techniques of IVF hadn't been perfected over the past quarter-century. These newer maneuvers, as well as all the others that most frighten people, begin with the same steps used for IVF: extraction of the eggs and sperm, fertilization in a petri dish, culture of the embryo until it reaches a certain stage and, finally, implantation into a receptive uterus. Of the scenarios that are now causing so much anxiety -- cloning, pre-implantation genetic diagnosis, genetic engineering of sex cells, the creation of human/animal hybrids, the culturing of human embryos as a source of replacement parts -- none is possible without the techniques of basic IVF: laboratory fertilization and embryo transfer.

Even if a slippery slope exists, it cannot be allowed to dictate science policy. Regulating something that can be done now on the basis of fears about what might be done later is a mistake. And it can result in some unintended and paradoxical effects. For all the railing against IVF in the '70s, the protests led to less control over IVF rather than more. Early on, opponents thought the best way to stop troublesome science was to keep the federal government from financing it, and they fought against using taxpayer money for research involving fetuses or embryos -- which, by extension, included IVF. One by one, a succession of bioethics commissions were formed to review these bans; one by one, the commissions recommended that the bans be lifted.

But politicians, some of whom were afraid of alienating a vocal anti-abortion lobby opposed to the experimental use of fetuses and embryos, generally did not want to hear that they should underwrite such controversial research. As a result, a pattern developed for the bioethicists' role in the regulatory minuet: sit on a commission, hold meetings, attend public hearings, write a report that says the research is ethically acceptable, have the report ignored, watch the next president or Congress convene a new commission, and repeat.

Even after the fetal research ban was lifted, and then the embryo research ban, the government still refused to sponsor IVF research. But the lack of federal support for IVF didn't stop scientists from working on it -- it just led them to carry on beneath the radar, out of the reach of the main mechanism for oversight, which was (and still is) the federal research grant and the standards it imposes on its recipients. If no one was getting government grants for IVF, then no one was being required to adhere to any standards. Entrepreneurial scientists were doing IVF anyway, bolstered by private money from infertile couples desperate for babies. Most of these scientists were honorable men and women with solid reputations and the loftiest of goals. A few, however, were motivated by the things that drive so many innovators, scientists included -- ego, curiosity, ambition, even greed. They were free agents who essentially did whatever they wanted and whatever the market would bear. Their efforts turned some of the fertility industry into a cowboy science driven by supply and demand.

Cloning is in many respects the contemporary version of cowboy science; cloners are today's daredevils and rogues, making claims of success that they have yet to document with genetic proof or even an actual baby. This is why so many politicians, here and elsewhere, have been trying so hard to put cloning in its place -- not by refusing to fund it, as happened to ill effect with IVF, but through legislation to ban it, whether the cloning takes place for research or for the sake of creating a cloned person.

They want to keep human cloning from going the way of IVF, which became part of the ordinary landscape simply because it was easier to ignore a controversial new technology than to regulate it. But they might be learning the wrong lesson -- and we all might be the poorer for it.

What legislators should learn from the IVF experience is that unfunded research will take place anyway, but in a less open and less coherent direction than might have occurred with government support. What they should be doing is not outlawing cloning, especially therapeutic cloning, but embracing it -- to encourage research that might lead to cures for dozens of degenerative diseases and to keep it from dangerously veering off down the slope that is so famously slippery.

As the world's first test tube baby turns 25, half a million others born through assisted reproductive technology can raise a glass in celebration of the new treatments for infertility that have subsequently developed. The agony of childlessness, for a couple that wants children, has been greatly eased because of the path blazed by Louise Brown's doctors, and her parents, too, who didn't even realize at first that they were involved in an enterprise that had never worked before. And look at all that has followed. Much of it might have been troublesome, but much more of it has been miraculous.

Happy birthday, Louise.

Robin Marantz Henig is a science writer whose new book, "Pandora's Baby: How the First Test Tube Babies Sparked the Reproductive Revolution," will be published early next year by Houghton Mifflin. She lives in New York City.

Louise Brown with her parents in 1979; and in April of this year.