Foetuses are more likely to show left-handed movements in the womb when their mothers are stressed, according to a new research.
Researchers at Durham University and Lancaster University in the UK said their findings are an indicator that maternal stress could have a temporary effect on unborn babies.
However, the researchers emphasised that the study was not evidence that maternal stress led to fixed left-handedness in infants after birth.
Using 4D ultrasound scans, researchers observed 57 scans of 15 healthy foetuses, recording 342 facial touches.
The foetuses were scanned at four different stages between 24 and 36 weeks of pregnancy. Researchers also asked the mothers of these babies how much stress they had experienced in the four weeks between each of the scans.
The researchers found that the more stress mothers reported, the more frequently foetuses touched their faces with their left hands.
A significant number of touches by the foetuses of stressed mothers were done with their left, rather than right hands – therefore foetal touches of their own faces, indicated a left-handed tendency.
As right-handedness is more common in the general population, the researchers had expected to see more of a bias towards right-handed movements in the foetuses as they grew older.
The high percentage of left-handed behaviour, observed only when mothers reported being stressed, led them to conclude that maternal stress has an effect on the lateral behaviour of the babies they scanned.
“Our research suggests that stressed mothers have foetuses who touch their face relatively more with their left hand,” said lead author Dr Nadja Reissland, in Durham University’s Department of Psychology.
“This suggests maternal stress could be having on effect on the child’s behaviour in the womb and highlights the importance of reducing maternal stress in pregnancy.
“Such measures may include increased emphasis on stopping stressful work early, the inclusion of relaxation classes in pre-natal care and involvement of the whole family in the pre-natal period.
“While we observed a higher degree of left-handed behaviour in the foetuses of stressed mothers than had been expected, we are not saying that maternal stress leads to a child becoming left-handed after birth, as there could be a number of reasons for this.
“The research does suggest, however, that a foetus can detect when a mother is stressed and that it responds to this stress,” said Reissland.
The findings are published in the journal Laterality: Asymmetries of Body, Brain and Cognition.