English schoolgirl Louise Joy Brown is about to celebrate her 10th birthday, a milestone for her and for in vitro fertilization, which since the girl's conception has given hope to infertile couples around the world while also raising ethical questions that won't go away.

Doctors and nurses in scrub suits the colors of sherbet wheeled another patient into the operating room for a brief procedure placing fertilized eggs in her womb.Everyone involved hoped they would cling there and grow into a pregnancy, but everyone knew they probably would not.

The scene played out on a video monitor over the heads of Georgeanna and Howard Jones, whose in vitro fertilization clinic gets credit for about 400 "test-tube babies," including the first in this country.

In a month, the woman on the screen would receive a phone call, telling her whether or not she was pregnant. Roughly three times in four, even at the best centers like the Jones Institute for Reproductive Medicine at Eastern Virginia Medical School, the answer is no.

Monday, it will be 10 years since in vitro technology was proven with the birth of Louise Brown in Britain, the first of an estimated 10,000 such infants born to infertile couples around the world.

In vitro fertilization has become routine medicine, a multimillion-dollar business and a catalyst of new ethical debate with each research advance.

At least 169 in vitro centers operate in 41 states in this country alone, and with the proliferation have come questions that practitioners and policy-makers are now being pressed to answer:

- Why isn't success more common?

- Are in vitro clinics and their practices adequately regulated?

- Why does in vitro cost so much - $4,000 to $6,000 on average per attempt - and should insurance companies or taxpayers help pay the bill?

- Why has the federal government maintained a de facto moratorium on financing research?

- Have some clinics taken advantage of a vulnerable patient population to make a profit?

"Some clinics are selling false hope," asserted Gary Ellis, director of a just-completed study of infertility for the congressional Office of Technology Assessment.

He and others stressed that only a minority of clinics fell into that category. But the vast market for infertility services - 2 million to 3 million American couples unable to have babies - enhances the danger of charlatanry and fraud.

"You can charge these people more, because they're more desperate," said Gina de Miranda, who founded a consumer protection group in Texas for infertile people after her own years of frustration and sadness.

Infertility treatments cost Americans $1 billion last year - $66 million of that for what has become the treatment of last resort, in vitro fertilization, according to the OTA study.

De Miranda, whose lobbying made Texas one of the five states, along with Maryland, Massachusetts, Hawaii and Arkansas, to require insurance companies to offer coverage of in vitro, advises anyone thinking of the procedure to ask questions.

Patients need to know more than the basics of in vitro: the hormonal stimulation of the woman to produce more than one egg in a month, the retrieval by doctors of as many eggs as possible, the mixing of those eggs with the husband's sperm in a petri dish, and the implanting of fertilized eggs, or embryos, in the uterus.

Patients should ask how long a program has been in operation, its rate of live births, how many retrieval procedures recover a mature egg, and how often the procedure is canceled before the embryo implant stage.

Success rates should be spelled out, the group said, stressing the need for clear definitions - for example, a "pregnancy" defined early in chemical terms may never produce a baby - and hard numbers.

A recent report by 41 U.S. in vitro centers claimed a combined rate of clinical pregnancy, determined by detectable fetal heartbeat, of 17 percent per embryo transfer. Calculating miscarriages and other loss, the chance of having a baby after one embryo transfer was 11 percent.

The centers surveyed were among the nation's most successful; scores of others still have recorded no births.

The Jones Institute reported that 500 patients underwent 736 stimulation cycles last year. In 537 cases, embryos were transferred. Of those, 169 clinical pregnancies occurred, or 23 percent per attempted stimulation; 29.5 percent per embryo transfer. The miscarriage rate was 24 percent.

Why have couples continued to pursue in vitro for a decade, despite its uncertainties?

The answer is in a portrait on the wall in Howard Jones' office, showing twinkly-eyed twin girls who'll be 3 next month: Heather and Ashley Smith.

The day the Jones Institute opened, Sarah Smith was at the door, the first to sign up for in vitro.

Seven failures later, however, she'd given up.

Still, her husband asked her to make one last try.

A month after the implant, the phone call from the clinic finally came. It was Christmastime - and Smith's present was two tiny heartbeats.