A new study shows that first time mothers who are older may increase their changes of living into their nineties, a new study shows.

Women who give birth to two-to-four children –instead of only one – increase their longevity as well, the study finds.

Researchers at the University of California San Diego School of Medicine looked at the relationship of age and longevity of 20,000 in the Women’s Health Initiative, a national study on women’s health that started in 1991.

The researchers, who followed the women for 21 years, found that approximately 54 percent of women survived to 90 years old.

The study also found that women who lived to age 90 were more likely to be college graduates, married, have a higher income and less likely to be obese or have a history of chronic disease.

“Our findings do not suggest that women should delay having a child, as the risk of obstetric complications, including gestational diabetes and hypertension, is higher with older maternal ages,” says lead author Aladdin Shadyab, adding, “It is possible that surviving a pregnancy at an older age may be an indicator of good overall health, and as a result, a higher likelihood of longevity.

Further research is needed to determine which social factors might explain associations of age at first childbirth and number of children with longevity, he adds of the study, which is published in American Journal of Public Health.