## **Core Concept**
Edward syndrome, also known as Trisomy 18, is a genetic disorder caused by an extra copy of chromosome 18. This condition leads to severe developmental delays, intellectual disability, and life-threatening medical problems. It is one of the most common chromosomal abnormalities.

## **Why the Correct Answer is Right**
The correct answer, , corresponds to Trisomy 18. This condition occurs when there is an extra copy of chromosome 18, resulting in a total of three copies instead of the usual two. This extra genetic material disrupts the normal development of the fetus, leading to the characteristic features of Edward syndrome. The features include severe intellectual disability, low birth weight, microcephaly (small head), overlapping fingers, and rocker-bottom feet.

## **Why Each Wrong Option is Incorrect**
* **Option A:** - This option refers to Trisomy 13, also known as Patau syndrome. While it is also a chromosomal abnormality, it involves an extra copy of chromosome 13, not chromosome 18.
* **Option B:** - This option could potentially refer to other genetic conditions or syndromes but does not specify Trisomy 18.
* **Option D:** - This option refers to Turner syndrome, which is a condition in females where one of the X chromosomes is missing or partially deleted. It does not involve chromosome 18.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that Edward syndrome (Trisomy 18) has a very poor prognosis, with most affected individuals not surviving beyond early childhood due to severe medical complications. The condition is also associated with a high rate of spontaneous abortion.

## **Correct Answer:** . Trisomy 18