Erythroblastosis foetalis occurs when a factor from mother passes into foetus through placenta

Options

A. Rh antigens
B. Agglutinins
C. Rh antibodies
D. ABO antibodies

Answer

**Step-by-Step Solution:**

1. **Understanding Erythroblastosis Foetalis**: Erythroblastosis foetalis is a condition that occurs when there is an incompatibility between the blood types of the mother and the fetus, particularly concerning the Rh factor.

2. **Identifying the Rh Factor**: The Rh factor is a specific antigen that can be present on the surface of red blood cells (RBCs). If the Rh antigen is present, the blood type is Rh positive; if absent, it is Rh negative.

3. **Role of the Mother’s Blood Type**: If a mother is Rh negative and the fetus is Rh positive, there is a risk of the mother's immune system producing antibodies against the Rh antigen after exposure to the Rh positive blood during delivery.

4. **Antibody Formation**: In the first pregnancy, the mother may not experience severe effects, but her body will produce Rh antibodies after exposure to the Rh positive blood during delivery. These antibodies are of the IgG type, which can cross the placenta.

5. **Impact on Subsequent Pregnancies**: In a subsequent pregnancy with another Rh positive fetus, the Rh antibodies produced in the mother’s body can cross the placenta and enter the fetal circulation. This can lead to the destruction of the fetus's red blood cells, causing anemia and other complications.

6. **Conclusion**: The factor responsible for erythroblastosis foetalis is the Rh antibodies produced by the mother in response to the Rh positive blood of the fetus. Therefore, the correct answer to the question is "Rh antibodies."

**Final Answer**: Rh antibodies.

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