[A case of fetal cystic hygroma. Clinical and echographic study].

In reference to a case of fetal cystic hygroma discovered on ultrasonogram, after 16 weeks of amenorrhea, the authors remind of the need for a karyotype; this is absolutely necessary in the therapeutic decision. Most of the time, it is related to a Turner's syndrome. In case of abnormal karyotype, a therapeutic interruption of pregnancy may be proposed. If the karyotype is normal, the ultrasonogram should be rechecked since hygroma regression has been described. If these images persist or become worse, it is related, most often, to a Noonan's syndrome and interruption of pregnancy may also be indicated.