A large testicle in a newborn is relatively common in newborn babies, and you can have your doctor determine if it is abnormal at the hospital. The more common causes are syringomyelia, and inguinal hernia. The details are as follows: 1. Syringomyelia: newborns found a large testicle, basically this is the reason, you can use a flashlight to see if it is permeable to light, if it is permeable to light is syringomyelia. This situation does not require additional treatment, as long as there is no continued change in size, usually around one year of age can be absorbed by themselves, but if more than one year of age, the syringomyelia is still very much this time you can go to the hospital to consider going to surgery, such as syringomyelia reversal surgery. 2. Inguinal hernia: this is the hernia that has always been commonly referred to as a hernia, the cause is the same as syringomyelia, but the difference is that the intestinal tube or the omentum enters the scrotum through the inner ring, the transillumination test is negative, and there is a gurgling sound of air and water when it is pressed. There may be other causes for a large testicle in a newborn, and prompt medical attention is recommended.