Aim: To evaluate the developmental pattern of fetal hand movements and facial activity and expression during the second and third trimester of pregnancy by four-dimensional ultrasound (4D-US). Subjects and methods: A total of 25 fetuses in uncomplicated pregnancies were analyzed; 15 fetuses at 13 to 16 weeks and 10 fetuses at 30 to 33 weeks of gestation were studied with abdominal 4D-US. After standard assessment in two dimensional (2D) real-time B mode, a 4D mode was switched on. Further examination lasted a maximum of 15 minutes. Results: Isolated hand movement and subtypes of hand movements were easily recognized by 4D-US. The subtypes of hand to head movement are: hand to head, hand to mouth, hand near mouth, hand to face, hand near face, hand to eye and hand to ear. All subtypes of hand to head movement can be seen from 13 weeks of gestation, with fluctuating incidence. Facial activities and different forms of expression are easily recognized by 4D-US. Among these, two types can be easily differentiated: smiling and scowling. Conclusions: 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.