Women who have twins tend to be healthier and longer-living than average, a study has found.
They also appear to be more fertile, with a longer reproductive age and a greater likelihood of giving birth.
Scientists based the findings on population records for more than 58,700 women from Utah, USA, born between 1807 and 1899.
Of the total, 4,603 had given birth to twins.
The study showed that for women born before 1870, mothers of twins were 7.6pc less likely to die each year after the age of 50.
Twinning women born between 1870 and 1899 had a non-significant 3.3pc reduced risk of dying.
"Having twins will not make you stronger or healthier, but stronger, healthier women are more likely to have twins naturally," said study leader Dr Shannen Robson. The findings are published today in the journal Proceedings of the Royal Society B.
"People are always interested in what affects how long we are going to live," said co-author Professor Ken Smith.
"It's complicated. There are so many factors that contribute to longevity, health and ageing.
"This study has been able to identify -- and it's a fairly novel result -- another important factor that contributes to health and longevity in later years, namely, that women bearing twins appear to be healthier."