The best period of gestation to carry out chorion villous biopsy for prenatal diagnosis is?
**Core Concept**
Chorion villous biopsy is a prenatal diagnostic test that involves sampling placental tissue to detect genetic abnormalities in the fetus. This procedure is typically performed between 10-12 weeks of gestation, a period when the embryo is still developing and the risk of miscarriage is relatively low.
**Why the Correct Answer is Right**
Between 10-12 weeks of gestation, the chorion villous biopsy can be safely performed, and the risk of miscarriage is significantly lower compared to earlier or later gestations. This time frame also allows for adequate time for the genetic analysis of the sampled tissue. The procedure involves the insertion of a catheter through the cervix under ultrasound guidance, and the placental tissue is then aspirated for genetic analysis.
**Why Each Wrong Option is Incorrect**
**Option A:** Performing chorion villous biopsy before 10 weeks of gestation increases the risk of miscarriage and may not provide accurate results due to the immature development of the placental tissue.
**Option B:** Performing chorion villous biopsy after 12 weeks of gestation may not be feasible due to the increased risk of miscarriage and the potential for the placenta to become more adherent to the uterine wall.
**Option C:** While chorion villous biopsy can be performed between 10-12 weeks of gestation, options A and B are not the correct answers.
**Clinical Pearl / High-Yield Fact**
Chorion villous biopsy is a relatively safe procedure when performed between 10-12 weeks of gestation, and the risk of miscarriage is significantly lower compared to earlier or later gestations.
**Correct Answer: C. 10-12 weeks of gestation.**