Research carried out by a North East university revealed how stress suffered by mums-to-be is transferred to their unborn babies.
It showed that foetuses are more likely to show left-handed movements in the womb when their mothers are under pressure.
The work was carried out at Durham and Lancaster universities. Staff there said it highlighted the importance of reducing stress during pregnancy.
Lead author Dr Nadja Reissland, in Durham University’s Department of Psychology, said: “Our research suggests that stressed mothers have fetuses who touch their face relatively more with their left hand.
“This suggests maternal stress could be having an 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 fetuses 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 fetus can detect when a mother is stressed and that it responds to this stress.”
Using 4d ultrasound scans, the 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.
The researchers found that the more stress mothers reported, the more frequently foetuses touched their faces with their left hands.
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 fetuses 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.
The findings are published in the journal Laterality: Asymmetries of Body, Brain and Cognition.