**Question:** Risk of damage to fetus by maternal rubella is maximum if mother gets infected in

A. first trimester
B. second trimester
C. third trimester
D. neither of the above

**Core Concept:** Rubella is a viral infection caused by the rubella virus, which belongs to the Togavirus family. In pregnant women, rubella infection can lead to congenital rubella syndrome (CRS) in the fetus, causing severe birth defects and developmental disabilities.

**Why the Correct Answer is Right:** The risk of damage to the fetus by maternal rubella is indeed highest when the infection occurs in the first trimester. This is because the rubella virus targets rapidly dividing cells, particularly in the first trimester, which is a time of significant fetal growth and organ development. If the infection occurs during this phase, the virus has the highest chance of crossing the placental barrier and causing CRS in the fetus.

**Why Each Wrong Option is Incorrect:**

A. Second trimester: Although the risk is lower in the second trimester, the virus can still cause CRS, especially if the infection occurs near the end of the second trimester or early in the third trimester.

B. Third trimester: While the risk is generally lower in the third trimester, the virus can still cause CRS if the infection occurs near the end of the third trimester or during labor and delivery.

C. Neither of the above: This option is incorrect because the risk of CRS is not zero at any stage of pregnancy. Even in the third trimester, the virus can cause CRS if the infection occurs at the right time.

**Clinical Pearl:** The importance of avoiding rubella infection during pregnancy is clearly demonstrated. Ensuring proper immunization in women of childbearing age and implementing strict infection control measures in healthcare settings are essential preventive measures to protect both pregnant women and their unborn children from the severe consequences of CRS.

**Correct Answer:** D. Neither of the above

**Explanation:** As mentioned earlier, the risk of damage to the fetus due to maternal rubella is not zero at any stage of pregnancy. While the risk is generally lower in the third trimester, rubella virus can still cause congenital rubella syndrome (CRS) if the infection occurs at the right time (first trimester). Thus, the correct answer is "Neither of the above," as the risk is not exclusively limited to the first trimester or third trimester but depends on the timing of maternal infection.