Background: Fetal Akinesia Deformation Sequence (FADS) is a rare, in most cases autosomal recessive, disorder. Its heterogeneous origin results in variable onset and expression of motor and postural anomalies. DNA-diagnostic possibilities are limited, thus prenatal diagnosis is chiefly dependent on sonographic examinations. Aim: To explore postural and motor development from a systematic sonographic protocol for fetuses at high risk for FADS. Specific questions are: which motor (i.e., specific movement patterns, quality and quantity of general movements) and postural aspects are most informative about emerging FADS and is the gestational age of onset range of FADS more limited for siblings? Methods: Ten families underwent 45, 15-minute sonographic assessments for motility and posture for ten index fetuses with FADS and nine subsequent pregnancies from five families. Results: FADS was diagnosed between 18 and 33 weeks gestation in ten index pregnancies and between 11 and 18 weeks gestation in 4/9 subsequent pregnancies, 1-12 weeks earlier than their index pregnancies. From the four assessment aspects, posture and movement quality were always abnormal, movement quantity in 7/14 and differentiation into specific movement patterns were reduced in comparison with healthy siblings (p < 0.01). Deterioration occurred in a 2 week period. Conclusions: Serial postural and qualitative assessments were most informative diagnosing FADS. Quantity and differentiation into specific movement patterns contributed substantially. Onset range of FADS within siblings was suggested to be more limited than between families. © 2009 Elsevier Ireland Ltd. All rights reserved.