**Core Concept**
The patient in question is likely suffering from a condition known as cryptorchidism, where one or both testes have not descended into the scrotum. This is a common condition in newborn males, affecting about 3-4% of full-term and 30% of preterm infants.

**Why the Correct Answer is Right**
The correct course of action is to advise the patient's parents to have their child undergo surgical intervention, specifically an orchidopexy, to bring the undescended testis into the scrotum. This procedure is usually performed between 6-18 months of age. The primary goal is to prevent potential complications such as testicular cancer, infertility, and torsion. Orchidopexy involves bringing the testis into the scrotum and securing it in place to prevent future complications.

**Why Each Wrong Option is Incorrect**
**Option A:** Immediate hormone therapy is not the first line of treatment for undescended testis. While hormone therapy may be used in some cases, surgery is generally the preferred method.

**Option B:** Waiting for spontaneous descent is not a recommended approach, as the likelihood of spontaneous descent decreases with age.

**Option C:** Routine ultrasound is not necessary for the diagnosis of undescended testis, as the diagnosis can be made clinically.

**Clinical Pearl / High-Yield Fact**
For exam purposes, it's essential to remember that undescended testis is a risk factor for testicular cancer and infertility. Early surgical intervention can help mitigate these risks.

**Correct Answer:** C.