Risk of the damage to the fetus by maternal rubella is maximum if the mother gets infected in –
**Core Concept**
The risk of congenital rubella syndrome (CRS) in the fetus is highest when the mother becomes infected during the first trimester of pregnancy, particularly between weeks 6 and 12. This period is critical for organogenesis, and maternal rubella infection can lead to severe congenital anomalies.
**Why the Correct Answer is Right**
During the first trimester, the fetus's organs and tissues are most vulnerable to the teratogenic effects of the rubella virus. The virus can cause damage to the developing eyes, ears, heart, and brain, leading to a range of congenital anomalies. The risk of CRS is highest when the mother is infected between weeks 6 and 12, as this is the period of organogenesis when the fetus's major organs are forming. The rubella virus can disrupt this process, leading to severe and potentially life-threatening congenital anomalies.
**Why Each Wrong Option is Incorrect**
**Option A:** Infection during the second trimester (weeks 13-26) is associated with a lower risk of CRS, as the major organs have already formed, and the risk of congenital anomalies is significantly reduced.
**Option B:** Infection during the third trimester (weeks 27-40) is associated with a very low risk of CRS, as the fetus's major organs have already formed, and the risk of congenital anomalies is minimal.
**Option C:** While maternal rubella infection can occur at any time during pregnancy, the risk of CRS is highest during the first trimester, particularly between weeks 6 and 12.
**Clinical Pearl / High-Yield Fact**
The risk of congenital rubella syndrome can be significantly reduced with vaccination of pregnant women against rubella, particularly during the first trimester. Vaccination is recommended for all pregnant women who have not previously been immunized against rubella.
**Correct Answer:** C.