A female with a family history of a genetic disorder became pregnant. Transabdominal chorionic villus sampling (CVS) can be done in:
First, I remember that CVS is a prenatal diagnostic test. The question is about the timing of the procedure. There are two approaches: transabdominal and transcervical. Transabdominal is usually done when the placenta is anterior, and the timing is important.
I think CVS is typically performed between 10 to 13 weeks of gestation. Wait, but some sources say 11 to 14 weeks. Let me confirm. The key point is that transabdominal CVS is done earlier than amniocentesis, which is around 15-18 weeks. So the options must be in the 10-13 week range.
Now, looking at the options (even though they aren't listed here), the correct answer would be a time in that window. Let's say the options are A. 8 weeks, B. 12 weeks, C. 16 weeks, D. 20 weeks. Then B would be correct. But since the user didn't provide the options, I'll proceed with the standard timing.
The core concept here is the gestational age for transabdominal CVS. The procedure is done in the first trimester, specifically between 10-13 weeks. Transabdominal approach is preferred when the placenta is positioned anteriorly and the uterine fundus is above the pubic bone, which is usually around this time. The placenta's position affects the approach choice.
Why is the correct answer in that window? Because earlier than 10 weeks might risk fetal loss, and after 13 weeks, the placenta might be too posterior, making transabdominal access difficult. Amniocentesis is later, so the options that are earlier or later than 10-13 weeks are incorrect.
Wrong options would be times outside this window. For example, 8 weeks is too early; the placenta isn't developed enough. 16 weeks is when amniocentesis is done. 20 weeks is too late for CVS.
Clinical pearl: Remember that CVS is done in the first trimester (10-13 weeks) for early diagnosis, while amniocentesis is second trimester. The transabdominal approach is used when the placenta is anterior, and the transcervical approach when it's posterior. Also, note that the risk of limb reduction defects is higher if done before 10 weeks, so timing is critical.
**Core Concept**
Chorionic villus sampling (CVS) is a prenatal diagnostic procedure to detect fetal chromosomal abnormalities. Transabdominal CVS is performed when the placenta is accessible via the abdominal route, typically in the **first trimester**. The optimal gestational age for transabdominal CVS is **10–13 weeks**, as placental villi are sufficiently developed, and fetal risk is minimized.
**Why the Correct Answer is Right**
Transabdominal CVS is performed between **10 and 13 weeks** of gestation. At this stage, the placenta is anterior (making abdominal