By Bruce Kennedy
CNN Interactive

On July 25, 1978, a British woman gave birth to a brown-haired, blue-eyed girl. Named Louise by her parents, she was perfectly normal -- and at the same time quite exceptional.

The birth of Louise Brown -- the first "test-tube baby" -- made international headlines. Her introduction into the world was the fruit of a decade of research by two doctors -- Robert Edwards and Patrick Steptoe. Working together, the men developed in vitro fertilization, or IVF.

The procedure involves removing eggs from a woman's ovary, fertilizing it in a laboratory dish filled with a man's sperm, and then placing the embryo into a woman's uterus -- where it develops into a fetus and, if all goes well, a child.

Louise's mother, Lesley, had damaged Fallopian tubes -- which prevented her from conceiving naturally. She and her husband, John, jumped at the opportunity to have a child.

"It was a chance," she said in an interview several years ago, "and when someone tells you there is a chance you can become pregnant, you only hear one thing -- the word 'pregnant' -- and you don't think about anything else."

Not only did the Browns have Louise, but they went on to have another daughter, Natalie, also through IVF.

The Brown daughters are just two of an estimated 500,000 children worldwide who are the result of IVF. Since 1978, science has made remarkable progress in what has come to be known as ART -- assisted reproductive technologies. There are now more than 300 fertility clinics in the United States alone that seek to help couples and single women who want children but are having trouble conceiving.

Dr. Hilton Kort, clinic director at Reproductive Biology Associates in Atlanta, says comparing the 1978 techniques with current methods "would be like driving a Model T Ford and driving a 1999 model car." The availability of reliable fertility drugs, which encourage ovulation, and a series of new medical procedures have increased the chances of patients getting pregnant by nearly tenfold in some cases.

One of the major recent breakthroughs in fertility procedures is intracytoplasmic sperm injection, or ICSI -- in which a single sperm is injected directly into an egg. Introduced in 1992, researchers see ICSI as a medical landmark.

"It was one of the biggest developments in ART," says Dr. David Adamson, president of the Society for Assisted Reproductive Technology. Adamson notes that in up to 50 percent of infertile couples, the male partner is either the sole cause -- or a contributing cause -- of infertility.

There is another procedure just coming into practice called blastocyst culture -- which, Kort says, is "very new and very exciting ... because we're going to be able to do some pretty incredible things with it."

The technique involves developing in the laboratory a blastocyst -- an embryo in its fifth or sixth day of development and made up of 150 to 200 cells -- and then implanting it in the uterus. By contrast, the more common in vitro fertilization technique involves 1- or 2-day-old embryos that, at that stage of development, are made up of only six to eight cells. In IVF, several of these younger embryos are implanted to ensure that at least one survives. The odds of a successful pregnancy are increased, but so are the odds of a multiple birth.

Blastocyst culture, on the other hand, implants only one or two of the older embryos. "So this way, you can't have more than twins," Kort notes.

These advances in ART have taken science and society into new ethical territory. In 1987, the Roman Catholic Church came out against IVF -- saying the procedure removed procreation from the marital context. The church also noted that human embryos created by IVF but not used were destroyed.

"As an industry we all recognize we have a societal responsibility," Kort says. "There are ethical issues and there are societal issues. We approach every single patient as an individual."

Recent headlines -- such as a 63-year-old woman giving birth after ART, women having septuplets and octuplets, or living sperm being extracted from comatose or dead men on behalf of their wives, lovers or families for future use -- have raised other issues. They also call into question what will happen in the next century -- when new techniques, including cloning, may well be available.

"How much do we want to allow or encourage parents to think of the making of babies as a process of 'making' rather than 'having?'" asked Glenn McGee of the University of Pennsylvania Center for Bioethics at a 1997 conference.

"I have argued in my work that research shows that children who are the product of high-technology pregnancies and neonatal care are more likely to think of their lives in different ways. The clone will be a different person. But how different? What will it feel like to be born as a child of this new era?"

As for Louise Brown, she is now 21, works at a nursery -- and well remembers being teased as a child by her schoolmates for her "test-tube baby" notoriety.

"People just have these visions of me being like sort of ... thin and .. long," she said in a recent interview with the London Daily Telegraph. "They thought that I grew in a test tube and then I just popped [my] head out."