Question

In which of the following weeks of pregnancy CVS is done:
A. ${12^{th}} - {14^{th}}$ week
B. ${8^{th}} - {10^{th}}$ week
C. ${5^{th}} - {7^{th}}$ week
D. None of these

Answer 1

Chorionic villus sampling (CVS) is a prenatal test used to detect particular defects in an unborn infant. A sample of cells from the placenta (the organ that connects the mother's blood supply to her unborn baby's blood supply) extracted and analysed for genetic abnormalities. It can be done only after chorionic villi and placenta are formed and embedded completely.

Complete explanation:
Option A ${12^{th}} - {14^{th}}$ week: It is a little late for this process because. If any defect found in CVS termination of pregnancy is later stage is quite difficult. So
Option A is not correct.
Option B in ${8^{th}} - {10^{th}}$ weeks: The risk of CVS resulting in problems, such as miscarriage or birth abnormalities in the infant, would be increased.
So, Option B is not correct.
Option C ${5^{th}} - {7^{th}}$ week: The branches of the umbilical vessels grow into the mesoderm; in this way, the chorionic villi are vascularized. Trophoblast, mesoderm, and blood vessels are present in the villi at this stage. As the development is still in progress CVS cannot be done.
Option C is not correct.
Option D: The chorionic villi created when the fertilised egg divides so, they have the same DNA as the embryo including any genetic abnormalities. Any chorionic villi deficiency will be present in the foetus. Week ${10^{th}} - {12^{th}}$ is the best time in pregnancy for CVS.
So, option D is correct.

Hence, Option D) is the correct answer.

Note:
Prenatal diagnosis means diagnosis before birth. It’s a way for your doctor to see if your developing baby has a problem. Amniocentesis and chorionic villus sampling are the two basic procedures (CVS). These tests help to find genetic disorders before birth.