Fetal facial development is essential not only for postnatal bonding between parents and child, but also theoretically for the study of the origins of affect. However, how such movements become coordinated is poorly understood. 4-D ultrasound visualisation allows an objective coding of fetal facial movements.
Interesting study analysing specific movements of facial muscles of fetuses in the womb thanks to 4D ultrasounds.
This research has shown that specific facial muscles movements could be linked to specific emotions helping babies communicate long before the language is developed.
More research should be done but we can maybe conclude that those fetal expressions become unconscious facial micro-movements in adults triggered by emotions and that there are universal across cultures
See on www.plosone.org