Researchers find a connection between left-handedness and low birth weight

May 15, 2018 by Bob Yirka, Medical Xpress report
Credit: CC0 Public Domain

A team of researchers from Finland, the Netherlands and Japan has found a connection between left-handedness and low baby birth weight. In their paper published in Proceedings of the National Academy of Sciences, the group describes their study of two large birth datasets and what they found.

Prior research has suggested a possible link between left-handedness and low . There have also been studies that suggest handedness develops before birth—fetuses as young as 10 weeks have been seen showing a preference for one thumb or the other on sonograms. In this new effort, the researchers sought to gather more evidence regarding birth weight and handedness. To that end, they obtained birth datasets—one from the Netherlands, the other from Japan. Noting that prior research has shown that left-handedness is more common in twins, and even more common in triplets, the researchers chose to focus their study exclusively on triplets. After filtering for triplets born at 33 weeks, the researchers pared down the datasets to 947 triplets in the one from the Netherlands and 1,305 from the one in Japan.

The researchers found that the average birth between left and right handers differed—for the Netherlands it was 1.79 kg on average for lefties, compared to 1.903 kg for right-handers. The results for the Japanese babies were similar—1.599 kg for lefties and 1.727 kg for right-handers. They noted also that the age of the mother did not seem to make any noticeable difference, nor did order. The researchers also discovered that those babies born left-handed were slower to reach major motor-skill milestones such as sitting, crawling and standing.

The researchers point out that their results do not indicate that is the sole cause of left-handedness. They note, for example, that past research has shown that heredity plays a role as well—left-handed people are more likely to have left-handed children, for example. They also acknowledge that their results do not really explain the bigger question of why approximately 10 percent of the population are born left-handed, or how it happens.

Explore further: Study finds link between handedness and mathematical skills

More information: Kauko Heikkilä et al. Triplets, birthweight, and handedness, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1719567115

Abstract
The mechanisms behind handedness formation in humans are still poorly understood. Very low birthweight is associated with higher odds of left-handedness, but whether this is due to low birthweight itself or premature birth is unknown. Handedness has also been linked to development, but the role of birthweight behind this association is unclear. Knowing that birthweight is lower in multiple births, triplets being about 1.5 kg lighter in comparison with singletons, and that multiples have a higher prevalence of left-handedness than singletons, we studied the association between birthweight and handedness in two large samples consisting exclusively of triplets from Japan (n = 1,305) and the Netherlands (n = 947). In both samples, left-handers had significantly lower birthweight (Japanese mean = 1,599 g [95% confidence interval (CI): 1,526–1,672 g]; Dutch mean = 1,794 g [95% CI: 1,709–1,879 g]) compared with right-handers (Japanese mean = 1,727 g [95% CI: 1,699–1,755 g]; Dutch mean = 1,903 g [95% CI: 1,867–1,938 g]). Within-family and between-family analyses both suggested that left-handedness is associated with lower birthweight, also when fully controlling for gestational age. Left-handers also had significantly delayed motor development and smaller infant head circumference compared with right-handers, but these associations diluted and became nonsignificant when controlling for birthweight. Our study in triplets provides evidence for the link between low birthweight and left-handedness. Our results also suggest that developmental differences between left- and right-handers are due to a shared etiology associated with low birthweight.

Related Stories

Study finds link between handedness and mathematical skills

May 5, 2016
A link between handedness and mathematical skills exists, but is more complex than is thought according to a study by the University of Liverpool.

More left-handed men are born during the winter, study says

July 3, 2014
Men born in November, December or January are more likely of being left-handed than during the rest of the year. While the genetic bases of handedness are still under debate, scientists at the Faculty of Psychology, University ...

The trials and tribulations of being left-handed

August 22, 2016
As 13 August is recognised worldwide as International Left-Handers Day, there has been an increased focus over the past week on the biological and genetic causes of left-handedness in humans, as well as the health, social ...

Right-or left-handedness affects sign language comprehension

May 9, 2017
The speed at which sign language users understand what others are 'saying' to them depends on whether the conversation partners are left- or right-handed, a new study has found.

Earnings show less for left-handed, says study

December 7, 2014
Much has been thrown at left-handed people—they are quick to anger, quickly scared and, with the exception of heads of state, are more or less life's losers. Much too has been bestowed upon left-handed people—they are ...

Recommended for you

Don't eat bitter pumpkin, study warns after women lose hair

May 25, 2018
A doctor warned Friday that bitter-tasting pumpkins and squashes can contain potent toxins, after two women were poisoned by their dinners and lost most of their hair.

Hot cars can hit deadly temperatures in as little as one hour

May 24, 2018
A lot can happen at 160 degrees Fahrenheit: Eggs fry, salmonella bacteria dies, and human skin will suffer third-degree burns. If a car is parked in the sun on a hot summer day, its dashboard can hit 160 degrees in about ...

Research finds a little exercise does a lot of good for ageing muscles

May 24, 2018
Getting old doesn't necessarily mean getting weak and frail – just a little bit of exercise can help maintain muscle mass and strength, Otago research has revealed.

In helping smokers quit, cash is king, e-cigarettes strike out

May 23, 2018
Free smoking cessation aids, such as nicotine patches and chewing gum, are a staple of many corporate wellness programs aimed at encouraging employees to kick the habit. But, new research shows that merely offering such aids ...

What makes us well? Diversity, health care, and public transit matter

May 23, 2018
Diverse neighbors. Health centers. Commuter trains. These community attributes, and other key factors, are linked to well-being and quality of life, according to Yale researchers.

Widely used e-cigarette flavoring impairs lung function

May 23, 2018
A new study has found that a common e-cigarette flavoring that has chemical characteristics similar to toxic chemicals found in cigarette smoke disrupts an important mechanism of the lungs' antibacterial defense system. The ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Digitalbookworm5678
not rated yet May 24, 2018
And I always thought it was because I came out ass first. Something my mother never forgave me for. (As if I did it on purpose.)

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.