The role of 4D US in evaluation of fetal movements and facial expressions and their relationship with fetal neurobehaviour.

The introduction of four-dimensional (4D) ultrasonography (US) allows the study of fetal movements and facial expressions in real time. The possibility of evaluating fetal movements has led to the study of fetal neurobehaviour, which has been for a long period of time a mystery for physicians. The study of fetal activity in utero could differentiate between normal and abnormal behavioural patterns, thus making possible the early recognition of fetal brain impairment. Facial expressions observed with 4D US represent a marker for neurobehaviour and at the same time could enhance fetal-maternal bonding. The present review represents an update of the literature on fetal movements, facial expressions, and their relationship with fetal neurobehaviour.