Women who give birth after 45 live longer than other women, Israeli researchers have found.

Researchers at Hadassah University Hospital, Ein Karem, found that at least four genes unique to women who conceive naturally after 45 generate an anti-aging effect on those women. The findings were the result of a genetic study of ultra-Orthodox Ashkenazi women from Mea She'arim who have at least six children.

"These findings are unique to Israel, and the group of women who give birth at a late age and carry the singular genes could explain the findings," said Neri Laufer, the chairman of Hadassah's obstetrics and gynecology department, who had a leading role in the study.

The DNA findings, which were recently reported at a Canadian Fertility and Andrology Society conference, could be the first step toward groundbreaking treatment that could help "rejuvenate the body" of women and men, said Laufer.

"Finding genes identified with the ability to conceive spontaneously at a late age can help us identify more women who carry these genes and are unaware of the possibility of conceiving at a late age," he said. "We also hope it will enable developing medical treatments that activate the genetic quality we identified in other women."

At least four of the genes identified by the researchers as part of a DNA fingerprint allowing women to give birth past 45 were found to inhibit apoptosis, or programmed cell death, generating an anti-aging effect in the women. Three additional genes found in the women are also associated with longevity.

The seven genes were among 60 that distinguished the DNA of women who conceived naturally after 45 from Ashkenazi women of the same age who had their last child by they time they were 30.

The mortality rate for 245,845 women who gave birth in Israel in the past several decades dropped the later the women gave birth to their last child, according to the researchers.

They found that the mortality rate for women with no children is 4.9 per 1,000. It dips to 3.4 among women who give birth by 35, 2.6 among women who give birth over 40, and 1.6 among women who give birth after 45.

The findings are a follow-up to earlier studies that showed that women's mortality rate was lower the more children they had, even among those with more than six children. The studies were first conducted in 1972, 1983 and 1995.

Laufer warned that women who delay having children could have difficulty getting pregnant, despite the reproductive technology available.

"Women should be aware that advancing their career at the expense of childbirth could come at the expense of reduced ability to conceive after the age of 35," he said.

A study of the Haredi women was first published in May 2004 in the journal Fertility and Sterility. Two years later, a team of Hadassah researchers studied Bedouin women who conceived naturally after 45.

Hospital researchers also conducted a study on mice to examine whether certain anti-aging proteins are secreted during pregnancy, making it easier for the body to rejuvenate itself.

They found that older pregnant mice - roughly comparable to women in their 40s - recovered from liver damage faster than mice that weren't pregnant.

"They found pregnancy leads to secreting a protein that enables the liver to recover faster," said Laufer. "Perhaps exposing older women who have trouble getting pregnant, or even men, to these proteins could rejuvenate the body and enhance its ability to recover at an older age."