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Handedness May Be Linked To Fertility

February 5, 2009

A new study suggests people who are “mixed-handed,” those who are able to use both hands with equal dexterity, may have a harder time conceiving a child than righties or lefties.

A study of more than 9,000 Danish couples showed that those in which one partner was mixed-handed, rather than exclusively right- or left-handed, tended to take slightly longer to conceive.

Mixed-handedness, also known as cross-dominance, is being able to do different tasks better with different hands. For example, mixed-handed persons might write better with their right hand but throw a ball more efficiently with their left hand.

Lead researcher Dr. Jinliang Zhu of the University of Aarhus in Denmark said the findings suggest that mixed-handedness and lower fertility may share a common cause.

Zhu told Reuters Health it was possible that hormonal exposure during prenatal development affects both a person’s eventual handedness and his or her fertility.

The researchers wrote in the medical journal Epidemiology that the theory needs further study.

But numerous studies in the past have looked at the connection between handedness and health, and several linked being left-handed or mixed-handed to having a higher risk of some diseases and disorders, including breast cancer, schizophrenia, dyslexia and autism.

It has been theorized that people who are not right-handed had some type of exposure that interfered with brain development in the womb, such as abnormal hormonal levels.

Zhu’s study concluded that mixed-handedness in both men and women were related to a longer time to conceive.

However, he said that while the study raises the possibility of the two having a common cause, other explanations are also possible.

He acknowledged that it is still unclear whether mixed-handedness is a signal that something went wrong during a person’s fetal development. “So far we know little about the origins of handedness,” Zhu said.

“At this time, it is difficult to say that mixed-handedness is pathological.”

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