**Question:** Genetic disorders are diagnosed at 11 weeks of pregnancy by:

**Core Concept:** Genetic disorders are conditions that arise from abnormalities in an individual's genes or chromosomes. These disorders can be caused by mutations, deletions, duplications, or translocations, leading to altered gene expression or function.

**Why the Correct Answer is Right:**

At 11 weeks of pregnancy, a fetal ultrasound can be performed to assess fetal growth, morphology, and overall well-being. One of the ancillary tests performed during this ultrasound is the **Nuchal Translucency (NT) measurement**. A higher than normal NT measurement (above the 95th percentile) can raise suspicion for genetic disorders.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Blood Sample):** Collecting a fetal blood sample is not a routine procedure during the 11-week ultrasound and can be invasive and risky for the fetus. Genetic testing via blood sampling is typically performed after the second trimester or at birth.

B. **Option B (Amniocentesis):** Amniocentesis involves drawing fluid from the amniotic sac for genetic testing. It is a more invasive procedure than blood sampling and is typically performed between weeks 15-20.

C. **Option C (Chromosome Analysis):** Chromosome analysis is a type of genetic testing that examines the number and structure of chromosomes. This test is usually performed after the 18-week ultrasound or later in pregnancy, not at 11 weeks.

D. **Option D (Fetal DNA Testing):** Fetal DNA testing, also known as non-invasive prenatal testing (NIPT), is a type of genetic testing that examines fetal DNA in maternal blood. It is a more recent method, typically performed after the 10th week of pregnancy.

**Clinical Pearl:** While fetal DNA testing has become more common in recent years, the correct answer is the nuchal translucency measurement (Option D) because it is a non-invasive procedure performed during the 11-week ultrasound. Nuchal translucency measurement helps assess the risk of genetic disorders, particularly trisomy 21 (Down syndrome).

Please note that the correct answer is not specifically related to genetic testing methods (A, B, C, and D). Instead, it focuses on a non-invasive ultrasound procedure (NT measurement) that detects increased risk for genetic disorders.