At the time of birth presence of which antibody indicates the infection of foetus (Intrauterine infection).

Options

A. lgG
B. lgD
C. lgM
D. lgA

Answer

To answer the question regarding which antibody indicates the infection of the fetus (intrauterine infection) at the time of birth, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question is asking which antibody's presence at birth indicates that the fetus has been infected during pregnancy.

2. **Identifying the Antibodies**: The four antibodies mentioned are:
- IgG
- IgD
- IgM
- IgA

3. **Understanding Immunoglobulins**: Immunoglobulins (Ig) are antibodies produced by the immune system to identify and neutralize pathogens like bacteria and viruses.

4. **Role of IgG**:
- IgG is the most abundant antibody in the blood and extracellular fluid.
- It is the only antibody that can cross the placenta from the mother to the fetus.
- The presence of IgG at birth suggests that the fetus has been exposed to an infection, as it indicates that the mother had an immune response to an infection that was transmitted to the fetus.

5. **Role of Other Antibodies**:
- **IgD**: Primarily functions in the initiation of B-cell activation and does not indicate fetal infection.
- **IgM**: Typically produced in response to an infection but does not cross the placenta effectively.
- **IgA**: Mainly found in mucosal areas and does not indicate fetal infection at birth.

6. **Conclusion**: Since IgG is the antibody that indicates intrauterine infection due to its ability to cross the placenta and its association with maternal infections, the correct answer is **IgG**.

### Final Answer:
The presence of **IgG** antibody at the time of birth indicates the infection of the fetus (intrauterine infection).

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