The authors report five ultrasonic imaging between 13 and 32 weeks of gestation. All of them have an hydrops fetalis and an aspect of like masses located in the nuchal region. A cystic retrocervical hygroma was confirmed at autopsy examination in three cases. The diagnosis of cystic hygroma remains inaccurate in the other two cases in the lack of the radiographic and anatomical verification. A review of the literature was made up to define the diagnostic aspects of the hygroma colli, their histological aspects and the mains etiological factors.