Fetal hand movements and facial expression in normal pregnancy studied by four-dimensional sonography

4D-US is superior over real-time two-dimensional ultrasound (2D-US) for qualitative, but inferior for quantitative analysis of hand movements. Thus 4D-US makes it possible to determine exactly the direction of the fetal hand, but the exact number of each type of hand movements can still not be determined. 4D-US is superior over two- and three-dimensional sonography in the evaluation of complex facial activity and expression. Among facial activities observed by 4D-US, simultaneous eyelid and mouthing movements dominate between 30 and 33 weeks of gestation. Pure mouth movements such as mouth opening, tongue expulsion, yawning and pouting are present, but at a significantly lower incidence. Facial expressions such as smiling and scowling can be precisely observed using 4D-US.