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

The core concept here is understanding the clinical features and diagnostic criteria of CRS. The main things to remember are the classic triad of symptoms: cataracts, congenital heart defects (like PDA), and hearing loss. Also, other features include microcephaly, developmental delays, and the presence of rubella IgM in the infant.

Now, the question is asking which statement is NOT true. The correct answer must be the one that doesn't fit. Let's think about the options. If one of the options says that the mother had rubella after 16 weeks of pregnancy, that's a red flag because the risk of CRS is highest when infection occurs in the first trimester. After 16 weeks, the risk drops significantly. So that would be the incorrect statement.

Another common wrong option might be about the presence of IgG in the infant. Infants can have IgG from the mother, but IgM is specific to their own infection. So if an option mentions IgG as a diagnostic marker, that's incorrect. Also, the classic triad must be present for a diagnosis. If an option says only two of the three are needed, that's wrong.

The clinical pearl here is to remember the timing of maternal infection and the diagnostic markers. High-yield fact: maternal infection in the first 20 weeks leads to CRS, with the highest risk before 12 weeks. Also, IgM in the infant is key for diagnosis.

So, putting it all together, the incorrect statement would be the one that says the mother was infected after 16 weeks, leading to CRS. That's the exception here.

**Core Concept**
Congenital rubella syndrome (CRS) occurs when maternal rubella infection crosses the placenta during pregnancy, typically before 20 weeks. Key features include cataracts, patent ductus arteriosus (PDA), and sensorineural hearing loss. Diagnosis relies on detecting rubella IgM in the infant or evidence of maternal infection during pregnancy.

**Why the Correct Answer is Right**
The incorrect statement in the question is likely the one claiming that maternal rubella infection after 16 weeks of gestation does **not** cause CRS. In reality, while the risk decreases after 16 weeks, maternal rubella infection **anytime before birth** can lead to CRS. However, the most severe manifestations occur if infection happens before 12 weeks. The correct answer hinges on this exception, as the question asks for the **false** statement.

**Why Each Wrong Option is Incorrect**
**Option A:** If it states that CRS causes cataracts, this is correct—cataracts are a hallmark of CRS.
**Option B:** If it mentions PDA as a cardiac defect in CRS, this is accurate—PDA is the most common heart defect in CRS.
**Option C:** If it claims rubella IgM is diagnostic in infants, this is true—IgM confirms recent intrauterine infection.
**Option D:** If it lists hearing loss as a classic feature, this is correct—sensorineural hearing loss is a cardinal sign.

**

✓ Correct Answer: D. Infection after 16 weeks of gestation result in major congenital defects