by Lizzie Parry
The babypod device was inserted into the vagina, to allow the unborn babies to listen to the music
And they were accompanied by specific mouth and tongue movements, which stopped when the music stopped.
Furthermore, 50 per cent of the foetuses reacted with a striking movement, opening their jaw very wide and sticking their tongue out as far as it would go.
In comparison, when a set of headphones were placed over a pregnant woman's bump, and the music was played through the abdomen, researchers observed no changes in foetal facial expression.
The researchers noted: 'Foetal response begins at 16 weeks, with statistically significant variations throughout the pregnancy.
'The further on the mother is in the pregnancy, the more striking the facial movements.
'Response is different for each foetus, with different response levels each time the music is played.'
They noted that twins showed similar behaviour.
They added: 'We are aware of and recognise the importance of talking to babies from the moment they are born to promote neurological stimulation.
'Now we have the amazing opportunity to do this much sooner, which is a huge advance.'
The study was published in the journal Ultrasound.