The recent efforts in the study of fetal compartments could help us to a better recognition of the proper fetal growth and well being. Fat content correlates directly with energy stores. Fat mass and lean body mass is often used in the nutritional assessment of the individual. Moreover chromosomal abnormalities may be detected by studying the fetal soft tissues of the neck, thus providing further proofs of the importance of evaluating the fetal body compartments. To obtain fat mass and lean mass, several measurements were proposed. We report a review of the literature on that topic.