The prenatal diagnosis of spermatic cord torsion is often really difficult and the diagnosis is usually retrospective. Herein, we report a case of a male newborn baby who presented at delivery with an enlarged, swollen and tender scrotum. US showed an enlarged right testis, with dishomogeneous texture, fluid collection between the testis and the tunica vaginalis and large hydrocele. Differential diagnosis included hydrocele complicated by infection or hemorrhage, testicular tumor or postnatal testicular torsion. Color and power Doppler did not reveal any flow signal, and the diagnosis of antenatal torsion with initial necrosis was made. The role of color Doppler US is emphasized in directing the patient to emergency surgical exploration, when testicular salvage may be possible. Delayed surgical treatment can be proposed, when the diagnosis of antenatal torsion has a high degree of certainty. However, the Doppler examination of a newborn baby's testis is a very difficult challenge even for an experienced radiologist.