**Question:** All are findings associated with the prenatal diagnosis for Down's syndrome except _____

A. Increased nuchal translucency
B. Short neck
C. Prominent tongue
D. Low set ears

**Core Concept:**
Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21. This leads to developmental delays, intellectual disability, and characteristic physical features. Prenatal diagnosis methods aim to identify individuals with Down's syndrome before birth, allowing for informed decision-making regarding continuation of pregnancy and preparation for postnatal care.

**Why the Correct Answer is Right:**
The correct answer is D. Low set ears, as this physical feature is not specific to Down's syndrome. Down's syndrome is associated with several other characteristics, including:

**Why Each Wrong Option is Incorrect:**
A. Increased nuchal translucency: This refers to the presence of an excessively thin layer of fluid in the nuchal region (the space between the skin and the base of the skull) during prenatal ultrasound examination. Increased nuchal translucency is a common finding in Down's syndrome and is considered a sensitive indicator of the condition.
B. Short neck: While Down's syndrome patients often exhibit short neck, this feature is not specific to the condition. Other causes of short neck, such as intrauterine growth restriction, can coexist with Down's syndrome.
C. Prominent tongue: Prominent tongue is a common feature in Down's syndrome patients; however, it is not exclusive to this condition. Other genetic disorders and growth abnormalities can also present with a prominent tongue.

**Clinical Pearl:**
Understanding the various features associated with Down's syndrome is essential for accurate prenatal diagnosis. It is crucial to recognize and interpret specific findings during ultrasound examinations to determine the likelihood of Down's syndrome and take appropriate actions, such as genetic testing, counseling, or monitoring of the pregnancy.

By assessing a combination of physical characteristics, ultrasound findings, and maternal age, prenatal diagnosis can increase the accuracy of detecting Down's syndrome and ensuring appropriate management of affected pregnancies.