A new test-tube baby method using eggs donated by younger women shows promise of extending the ability of women to have babies through their 40s or beyond, researchers said.

"It was kind of phenomenal," Dr. Mark Sauer said of the results of a study involving seven women ages 40 to 44 with non-functioning ovaries who received embryos created from their husbands' sperm and the eggs of younger women.Six of the recipients became pregnant, resulting in the births of five children, one miscarriage and one stillbirth. Their pregnancy rate was about three times better than that achieved in most in-vitro fertilization programs, said Sauer, of Women's Hospital and the University of Southern California in Los Angeles.

The study indicates "a woman's reproductive life does not have to end at 40 and probably goes well into the fifth decade," he said. For women in good health who receive good medical care this may be "a new chapter in the biological clock phenomenon," Sauer said.

In an editorial accompanying the report, published Wednesday in The New England Journal of Medicine, executive editor Dr. Marcia Angell said the "limits on the childbearing years are now anyone's guess; perhaps they will have more to do with the stamina required for labor and 2 a.m. feedings than with reproductive function."

Although the study adds another twist to ethical and legal controversies swirling around new reproductive technologies, Angell noted that these methods help infertile couples have children who are "badly wanted and greatly prized." As such, "It is hard to object to this," she added.

American women increasingly have been delaying childbirth to later in life, when the risk for birth defects goes up and the ability to conceive a child decreases. Sauer said the new research promises to help women in their 40s or even 50s whose ovaries have stopped functioning because of menopause to have babies.