Dr Viola Marx, a psychologist at the University of Dundee, was the lead author of the study, published in the journal Infant Behaviour And Development.
She said: "Mothers spontaneously and also intentionally touch their abdomen during pregnancy, often to communicate with the foetus.
"Any stimulation can be beneficial to the development of the foetus and bonding of the mother, father and the foetus."
Oddly, the unborn babies responded more to a stranger's touch than their father's.
Dr Marx said previous research had shown unborn babies also respond when their mother talks to them, helping them recognise her voice after birth.