**Core Concept**
Trisomy 18 is a chromosomal disorder characterized by an extra copy of chromosome 18, leading to severe developmental and physical abnormalities.

**Why the Correct Answer is Right**
Trisomy 18 occurs due to a meiotic error during the formation of gametes, resulting in an abnormal number of chromosomes. This condition is associated with a high risk of miscarriage, stillbirth, and infant mortality. The affected individuals often exhibit severe growth restriction, microcephaly, rocker-bottom feet, and characteristic facial features.

**Why Each Wrong Option is Incorrect**
**Option A:** Edwards syndrome is a different chromosomal disorder, characterized by trisomy 18p, which is a partial trisomy involving the short arm of chromosome 18. This option is incorrect because Edwards syndrome is not the same as Trisomy 18.
**Option B:** Down syndrome is caused by trisomy 21, not trisomy 18. This option is incorrect because it refers to a different chromosomal disorder.
**Option C:** Patau syndrome is another chromosomal disorder, characterized by trisomy 13, not trisomy 18. This option is incorrect because Patau syndrome is distinct from Trisomy 18.

**Clinical Pearl / High-Yield Fact**
Trisomy 18 is also known as Edwards syndrome, named after John Hilton Edwards, who first described the condition in 1960. It is essential to recognize the characteristic features of Trisomy 18 to provide accurate prenatal diagnosis and counseling.

**Correct Answer:** C. Patau syndrome is incorrect, the correct answer is Edwards syndrome, however Edwards syndrome is the correct answer in this scenario, Trisomy 18 is Edwards syndrome