Okay, let's tackle this question about congenital rubella. The user wants me to explain why a particular option is incorrect and the others are correct. First, I need to recall the key facts about congenital rubella syndrome (CRS).

The core concept here is understanding the clinical features, transmission, and complications of CRS. The question is asking which statement is NOT true. So I need to remember the typical manifestations and exceptions.

Congenital rubella is caused by maternal infection during pregnancy, especially in the first trimester. The classic triad includes cataracts, heart defects, and deafness. Other features might be growth retardation, hepatosplenomegaly, and thrombocytopenia. Also, the virus can persist in the body for years, making the IgM antibody a marker for recent infection.

Now, the correct answer is the one that's an exception. Let's think about possible incorrect statements. For example, if an option says that "Congenital rubella can be transmitted by a mother infected in the third trimester," that would be incorrect because the risk is highest in the first trimester. Another wrong option might claim that "IgG antibody is present in the newborn but disappears within weeks," but actually, IgG persists longer. Also, maybe a statement about the vaccine being live attenuated but contraindicated in pregnancy, which is true, so if an option says it's safe during pregnancy, that's wrong.

Each wrong option needs to be addressed. For example, if option A says CRS causes mental retardation, that's correct. If option B states that rubella vaccine is contraindicated in pregnancy, that's correct. If option C claims that the virus is not shed postnatally, that's incorrect because the virus can be shed in urine for up to a year. If option D says that congenital heart defects are rare, that's wrong because they're common in CRS.

The clinical pearl here is to remember the first trimester is most critical for CRS development and that IgM detection is key for diagnosis. Also, the live vaccine's contraindication during pregnancy is crucial to avoid fetal infection.

Putting it all together, the correct answer is the option that incorrectly states transmission in the third trimester or something similar. Then, explain why each wrong option is incorrect based on known facts. The clinical pearl reinforces the importance of the first trimester and IgM testing.

**Core Concept**
Congenital rubella syndrome (CRS) results from maternal rubella infection during pregnancy, particularly in the first trimester. It causes a spectrum of fetal abnormalities, including cataracts, cardiac defects, and sensorineural deafness, due to direct viral cytopathic effects and immune-mediated injury.

**Why the Correct Answer is Right**
The incorrect statement is likely one that contradicts established pathophysiology. For example, if an option claims "Congenital rubella is not associated with deafness," this is false, as auditory nerve damage is a hallmark of CRS. The virus persists in the inner ear, leading to progressive sensorineural hearing loss.

**Why Each Wrong Option is Incorrect**
**Option A:** If it states "CRS causes cataracts due to lens inflammation," this is correct—rubella virus infects the lens, causing opacification.
**Option B:** If it

✓ Correct Answer: D. Increased risk of congenital malformation if infection occur after 16 weeks.