**Question:** Chorionic villous sampling done before 10 weeks may result in -

A. Maternal hemorrhage
B. Fetal demise
C. Infection
D. Oligohydramnios

**Core Concept:** Chorionic villous sampling (CVS) is a prenatal diagnostic test used to determine fetal chromosomal abnormalities, infections, and other genetic and structural anomalies. It involves obtaining a tissue sample from the placenta (chorionic villi) for laboratory analysis. CVS is usually performed between 10 and 13 weeks of gestation, with the risk of complications decreasing as the procedure is done earlier in pregnancy.

**Why the Correct Answer is Right:** Chorionic villous sampling before 10 weeks increases the risk of complications due to several reasons:

1. **Maternal hemorrhage:** As the gestational age decreases, the placenta becomes less developed and vascular, which increases the risk of excessive bleeding during the procedure.
2. **Fetal demise:** Performing CVS earlier in pregnancy increases the chance of causing fetal demise due to the higher risk of damaging the fetus during the procedure or introducing infection or toxins into the maternal bloodstream.
3. **Infection:** CVS before 10 weeks increases the risk of infecting the fetus with maternal pathogens, which can lead to severe complications like sepsis or congenital infections.
4. **Oligohydramnios:** Early CVS may result in decreased amniotic fluid volume (oligohydramnios) due to the procedure affecting the fetal renal system or disrupting the normal amniotic fluid circulation.

**Why Each Wrong Option is Incorrect:**

1. **Option A (Maternal hemorrhage):** Although hemorrhage is a possibility, CVS is generally considered safe in experienced hands. However, it increases the risk as gestational age decreases.
2. **Option B (Fetal demise):** CVS before 12 weeks is associated with a higher risk of causing fetal demise. After 12 weeks, the risk decreases considerably, but the procedure remains invasive and carries some risks.
3. **Option C (Infection):** While CVS can introduce pathogens into the uterine cavity, the risk is higher when performed earlier in pregnancy. After 12 weeks, the risk of infection decreases.
4. **Option D (Oligohydramnios):** CVS might lead to oligohydramnios, but the risk is higher at earlier gestational ages. After 12 weeks, the risk decreases.

**Clinical Pearls:**

- CVS is generally performed between 10 and 12 weeks of gestation, ensuring a safer procedure for both the mother and the fetus.
- Timing is crucial for minimizing complications, and performing CVS at an earlier gestational age increases the overall risk for both maternal and fetal complications.
- Comprehensive counseling and informed consent are essential before performing CVS, particularly for patients with a high-risk pregnancy.