NEW YORK — Lesley Brown, the mother of the world’s first ‘‘test-tube baby,’’ died June 6 in Bristol, England. She was 64.

Her death, at the Bristol Royal Infirmary, was caused by complications of a gallbladder infection, said Michael Macnamee, executive director of the Bourn Hall Clinic in Cambridge, where the in vitro fertilization technique that produced her daughter Louise was developed by Robert G. Edwards and Dr. Patrick Steptoe. Her death was not widely reported at first.

Louise Brown’s birth on July 25, 1978, was an instant global sensation and a turning point in the treatment of infertility, offering hope to millions of couples who had been unable to have children. Since then, more than 4 million babies worldwide have been born through in vitro fertilization, in which sperm and eggs are mixed outside the body and the resulting embryos are transferred into the womb.

In some developed countries, those methods now lead to about 3 percent of all live births, Macnamee said. In 2010, about 59,000 births in the United States resulted from in vitro procedures, according to the Society for Assisted Reproductive Technology.

In vitro fertilization is an established treatment now, but it had a long, slow and rocky start. The research by Edwards, a biologist, and Steptoe, a gynecologist, had gone on for 10 years, and the treatment had failed in about 60 couples by the mid-1970s. It had produced only one pregnancy, and that one was ectopic — growing in a fallopian tube instead of the uterus — and had to be aborted.

Then Lesley Brown and her husband, John, came along. She was a homemaker, he a railroad employee. They had been trying for nine years to conceive a child.

In vitro fertilization was ‘‘an incredible leap into the unknown,’’ Macnamee said. Even if a pregnancy did result, would the baby be healthy? Critics of the research had predicted that the treatment could lead to terrible abnormalities. But Mrs. Brown was determined.

“Every breakthrough in medical science requires somebody to put themselves forward with the passion and commitment she had,’’ Macnamee said.

Mrs. Brown became pregnant on the first try. Once the news got out, public fascination with her case was unrelenting. She was a quiet woman, Macnamee said, and the attention stunned her.

After Louise’s birth, the Browns went home from the hospital to find reporters camped out on their street. For months Lesley Brown could not leave the house without being chased, so the family moved to another house with a backyard, allowing her to take Louise outside in peace.

Four years later they had another daughter, Natalie, also conceived by in vitro fertilization, also on the first try.

John Brown died in 2007 at 64. Lesley Brown leaves her two daughters and three grandchildren.

It took time for in vitro fertilization to gain acceptance. Fears that it could harm mothers and children lingered. Early success rates were low, and there were moral objections from some religious groups that viewed the creation of human life in a laboratory as a violation of the sacred order.

But overall the techniques have proved safe, and success rates have climbed to rival those of natural conception.

Some religious objections remain, however. The Roman Catholic Church, for instance, continues to condemn in vitro fertilization.

In 2010, at 85, Edwards received the Nobel Prize in Physiology or Medicine. But he had declined mentally and was not ‘‘in a position to understand the honor,’’ Macnamee told The New York Times when the prize was announced. Steptoe did not share the award because he had died in 1988, and Nobel Prizes are not given posthumously.