## **Core Concept**
Chorionic villus sampling (CVS), also known as chorionic villus biopsy, is a prenatal test that involves removing a small sample of cells from the placenta for genetic testing. The primary purpose is to detect chromosomal abnormalities or other genetic disorders early in pregnancy. The procedure carries several potential risks.

## **Why the Correct Answer is Right**
The correct answer, **C. **, is related to the risk of **miscarriage**, which is a well-known complication of CVS. This risk is attributed to the invasive nature of the procedure, which may cause disruption to the pregnancy. The risk of miscarriage following CVS is estimated to be around 1 in 300 to 1 in 500. This procedure involves inserting a catheter through the cervix or a needle through the abdomen to collect placental tissue, which may cause irritation or injury to the uterus or placenta, potentially leading to miscarriage.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because while certain infections could potentially be a risk with any invasive medical procedure, CVS is not specifically highlighted for causing infections as a primary hazard compared to the risk of miscarriage.
- **Option B:** This option is incorrect because while there could be theoretical risks related to the placenta and its function, the direct and most commonly acknowledged hazard of CVS is not placental insufficiency as a broad or primary risk.
- **Option D:** This option is incorrect because, although chromosomal mosaicism can be a consideration in prenatal testing, the hazard or risk directly associated with the procedure itself (like CVS) is more directly related to physical complications such as miscarriage rather than the informational complications like mosaicism.

## **Clinical Pearl / High-Yield Fact**
A key point to remember about CVS is that it is typically performed between 10 to 12 weeks of gestation. A significant clinical pearl is that CVS can provide valuable information about the fetus's genetic makeup early in pregnancy, which can help in making critical decisions. However, candidates should always counsel patients about the risk of miscarriage associated with the procedure.

## **Correct Answer: C. Miscarriage.**