In erythroblastosis foetails,

Options

A. Rh antibodies pass from the Rh(+ve) mother into the Rh(-ve) baby through the placenta .
B. Rh antibodies pass from the Rh(-ve) mother into the Rh(+ve) baby through the placenta.
C. Rh antigens pass from the Rh(-ve) mother into the Rh(+ve) baby through the placenta.
D. Rh antigens pass from the Rh(+ve) mother into the Rh(-ve) baby through the placenta.

Answer

**Step-by-Step Solution:**

1. **Understanding Erythroblastosis Fetalis:**
Erythroblastosis fetalis is a condition that occurs when there is an incompatibility between the blood types of the mother and the fetus, specifically concerning the Rh factor. This condition is most commonly seen when an Rh-negative mother carries an Rh-positive fetus.

2. **Rh Factor Basics:**
The Rh factor is a protein that can be present on the surface of red blood cells. If a person has this protein, they are considered Rh-positive; if they do not, they are Rh-negative.

3. **Pregnancy Scenario:**
If an Rh-negative mother conceives a child with an Rh-positive father, the child will inherit the Rh-positive trait. During the first pregnancy, the mother may not have developed antibodies against Rh antigens because the fetal blood does not typically mix with maternal blood until delivery.

4. **Sensitization Process:**
At the time of delivery, if the Rh-positive fetal blood enters the mother's circulation, her immune system may recognize the Rh antigens as foreign and produce antibodies against them. This process is called sensitization.

5. **Subsequent Pregnancies:**
In subsequent pregnancies, if the mother becomes pregnant with another Rh-positive child, the antibodies she produced during the first pregnancy can cross the placenta and attack the fetal red blood cells, leading to hemolysis (destruction of red blood cells).

6. **Conclusion:**
This leads to the condition known as erythroblastosis fetalis, where the fetus may suffer from severe anemia, jaundice, or even fetal death due to the destruction of its red blood cells.

7. **Correct Answer:**
Based on the above understanding, the correct answer to the question is:
**B. Rh antibodies pass from Rh-negative mother into the Rh-positive baby through the placenta.**

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