Introduction. The objective is to report a case of Cornelia de Lange syndrome (CdLS) diagnosed by detailed observations using three-dimensional sonography. Case Report. A 33-year-old healthy multipara was referred to our hospital at 34-week gestation after severe fetal growth restriction, congenital heart anomaly, and antebrachium abnormality were diagnosed during the third trimester. Further sonography diagnosis on cardiac abnormalities diagnosed the existence of ventricular septal defect in the outflow tract, atrioventricularis communis, and truncus arteriosus communis where the pulmonary artery branched from the common arterial trunk. As for abnormalities of the forearms, ectrodactylia and monodactylism were suspected and the abnormalities were observed sterically by using three-dimensional sonography. A 1986 g (1.07 percentile) male newborn was delivered by assisted breech extraction at 37-week gestation. After birth, from characteristic facies including bushy eyebrow, broad nasal bridge, micrognathia, and abnormalities of the forearms (ectrodactylia and monodactylism), the case was diagnosed with CdLS. Conclusion. Through detailed observation including abnormalities of fingers, we could exemplify this very rare disease as an antenatal diagnoses for fetal growth retardation.