**Core Concept**
Toxoplasmosis is a parasitic infection caused by *Toxoplasma gondii*, which can be transmitted vertically from mother to fetus, especially if the mother is not compliant with antiparasitic therapy during pregnancy. This vertical transmission can lead to congenital toxoplasmosis, characterized by a range of clinical manifestations, including cerebral calcification and hydrocephalus.

**Why the Correct Answer is Right**
Toxoplasmosis is known to cause cerebral calcification due to the presence of calcified cysts in the brain tissue. The calcification is a result of the parasite's ability to form cysts within the brain, which can lead to a range of neurological symptoms, including hydrocephalus. Spiramycin, an antibiotic commonly used to treat toxoplasmosis in pregnant women, was prescribed to the mother in this scenario, but her non-compliance with therapy likely led to the vertical transmission of the parasite to the fetus. The characteristic cerebral calcification and hydrocephalus seen in congenital toxoplasmosis are a result of the parasite's ability to infect the developing fetus's brain.

**Why Each Wrong Option is Incorrect**
**Option A:** Rubella, caused by the Rubella virus, is a different type of congenital infection that can lead to a range of clinical manifestations, including ophthalmologic, cardiac, and auditory abnormalities, but it is not typically associated with cerebral calcification and hydrocephalus.

**Option C:** CMV (Cytomegalovirus) is another common congenital infection that can cause a range of clinical manifestations, including neurological symptoms such as hearing loss and developmental delay, but it is not typically associated with cerebral calcification and hydrocephalus.

**Option D:** Herpes simplex virus can cause congenital infection, leading to a range of clinical manifestations, including skin, eye, and central nervous system symptoms, but it is not typically associated with cerebral calcification and hydrocephalus.

**Clinical Pearl / High-Yield Fact**
It is essential to note that spiramycin is a macrolide antibiotic that is commonly used to treat toxoplasmosis in pregnant women, but it is not a curative treatment and should be used in conjunction with other antiparasitic therapy to prevent vertical transmission of the parasite.

**✓ Correct Answer: B. Toxoplasmosis**