**Core Concept**
Nuchal translucency (NT) is a measurement of the sonographic appearance of the subcutaneous tissue at the back of the fetal neck, typically performed between 11 and 14 weeks of gestation. It is an important marker for the risk of aneuploidy and other fetal anomalies.

**Why the Correct Answer is Right**
An NT thickness of 3.5 mm or greater at 14 weeks is suggestive of an increased risk of Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and other chromosomal abnormalities. The pathophysiology underlying this association is not fully understood, but it is thought to be related to the altered fluid dynamics and lymphatic drainage in the fetal neck. The increased NT thickness may also be associated with cardiac and other congenital anomalies.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because a normal NT measurement does not rule out Down syndrome or other chromosomal abnormalities.
**Option B:** Incorrect because an NT measurement of 3.5 mm or greater is not specific to fetal cardiac anomalies.
**Option C:** Incorrect because an NT measurement of 3.5 mm or greater is not directly related to fetal lung maturity.

**Clinical Pearl / High-Yield Fact**
A nuchal translucency thickness of 3.5 mm or greater at 14 weeks is associated with a 1 in 50 risk of Down syndrome. This is why NT measurement is often used as a screening test in conjunction with maternal serum markers and fetal ultrasound examination.

**Correct Answer:** C. Increased risk of Down syndrome, Edwards syndrome, and other chromosomal abnormalities.