In a retrospective study of Utah pioneers, scientists discovered that women who deliver twins live longer, have more children than expected, bear babies at shorter intervals over a longer time, and are older at their last birth, compared to other mothers.
The revelation does not necessarily mean that it is healthy for women to have twins, rather, that healthier women have a increased chance of delivering twins (not accounting for fertility interventions).
“Having twins will not make you stronger or healthier, but stronger, healthier women are more likely to have twins naturally,” said Shannen Robson, Ph.D., the study’s first author.
Researcher Ken R. Smith, Ph.D., added: “The prevailing view is that the burden of childbearing on women is heavier when bearing twins. But we found the opposite: women who naturally bear twins in fact live longer and are actually more fertile.”
The study is published online in the journal Proceedings of the Royal Society B.
Researchers reviewed data for 58,786 non-polygamous Utah women who were born between 1807 and 1899, lived to age 50 and married once after 1850 to husbands who were alive when their wives were 50.
Of those, 4,603 were the mothers of twins and 54,183 gave birth only to one baby at a time.
The records came from the Utah Population Database, which is among the world’s most comprehensive computerized genealogies and includes vital records of largely Mormon migrants to Utah and their Utah descendants.
Implications of Twinning as an Indicator of Health
“People are always interested in what affects how long we are going to live,” said Smith, who directs the University of Utah’s Pedigree and Population Resource, which maintains and manages the Utah Population Database. “It’s complicated. There are so many factors that contribute to longevity, health and aging.”
“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,” Smith said.
“That innate healthiness is contributing to their ability to have twins, and it is also contributing to their longevity.”
However, he emphasizes that the study looked at women who lived past menopause, not those who died earlier, perhaps in childbirth.
“We do know women who have twins, triplets and so on do have medical complications and their health is sometimes compromised,” Smith said. “But we are talking about the long view.”
“Women having children are fundamentally young and healthy,” he said.
“So the risk of dying in childbirth is quite low. The women who have twins have a somewhat elevated risk of mortality over those [child-bearing] years, but the vast majority of those women reach age 50, and we’re able to observe that they have healthier lives.”
While twinning sometime runs in families, previous studies have shown environmental factors are more important – factors such as greater health in the mother or childbearing at later ages, which are more likely to produce twins.
The study was designed to look at the effects of natural births of twins, and the study population lived before birth control and treatments for infertility were available.
“We’re saying that women who twin naturally have something that makes them healthier,” said Smith.
“We are able to see that in these ancestral women because they had many children and had no fertility treatments. They have left a legacy through their descendants who may all share this desirable trait of being healthier.”
For women today “who have access to infertility treatment and who have twins – which isn’t uncommon – we simply don’t know how that will affect their health,” he added.
“We’re not encouraging women to actively seek having twins so they can live longer. It’s not a conclusion we can draw.”
Source: University of Utah