**Core Concept**
Amniocentesis is a prenatal diagnostic procedure that involves withdrawing a sample of amniotic fluid to detect genetic abnormalities or chromosomal disorders in the fetus. The timing of amniocentesis is crucial to obtain accurate results.

**Why the Correct Answer is Right**
Amniocentesis is typically performed between 15 and 20 weeks of gestation. This period allows for the detection of chromosomal abnormalities, such as Down syndrome, through the analysis of fetal cells in the amniotic fluid. The procedure is usually done after the 15th week to minimize the risk of miscarriage and to ensure that the amniotic fluid contains sufficient fetal cells for analysis.

**Why Each Wrong Option is Incorrect**
**Option A:** Performing amniocentesis before 15 weeks increases the risk of miscarriage and may not provide accurate results due to the presence of maternal cells in the amniotic fluid.
**Option B:** Doing amniocentesis after 20 weeks may not be feasible in some cases due to the decreased volume of amniotic fluid and the increased risk of complications.
**Option C:** There is no specific evidence to support amniocentesis being performed at 10 weeks, making it an incorrect option.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that amniocentesis should be performed between 15 and 20 weeks of gestation to ensure accurate results and minimize the risk of complications.

**Correct Answer: C. 16-18 weeks.**