True about chorionic villi biopsy:a) Strongly associated with fascio mandibular defectsb) Done in 10-12 weeksc) Rh immunoglobulin prophylaxis is not necessaryd) Done to diagnose genetic disorders
**Core Concept**
Chorionic villi biopsy, also known as chorionic villus sampling (CVS), is a prenatal diagnostic procedure that involves removing a small sample of placental tissue for genetic testing. This procedure is typically performed between 10-12 weeks of gestation to diagnose chromosomal or genetic abnormalities in the fetus.
**Why the Correct Answer is Right**
CVS is a widely accepted method for diagnosing genetic disorders, such as Down syndrome, cystic fibrosis, and other chromosomal abnormalities. The procedure involves inserting a thin catheter through the cervix and into the placenta to collect a sample of chorionic villi, which are then analyzed for genetic material. This allows for early detection and diagnosis of genetic disorders, enabling parents to make informed decisions about their pregnancy.
**Why Each Wrong Option is Incorrect**
**Option A:** Fascio mandibular dysostosis (also known as Treacher Collins syndrome) is a rare genetic disorder that affects the development of the face and ears, but it is not strongly associated with chorionic villi biopsy.
**Option B:** While CVS is typically performed between 10-12 weeks of gestation, this is not a specific characteristic of the procedure, and it is not the correct answer.
**Option C:** Rh immunoglobulin prophylaxis is actually necessary for women who are Rh-negative and are pregnant with an Rh-positive fetus, as it helps prevent the formation of antibodies against Rh-positive blood. CVS may pose a risk of Rh sensitization, so prophylaxis is indeed necessary in some cases.
**Clinical Pearl / High-Yield Fact**
Chorionic villi biopsy is a valuable tool for diagnosing genetic disorders, but it carries a small risk of miscarriage and other complications. It is essential for women to discuss the risks and benefits of CVS with their healthcare provider before undergoing the procedure.
**Correct Answer: D. Done to diagnose genetic disorders**