An Rh-positive male gets married to an Rh-negative female. During their second pregnancy, which of the following events would be observed ?

Options

A. Rh incompatibility disease
B. Erythroblastosis foetalis
C. Muscular dystrophy
D. Both ( A) and (B)

Answer

### Step-by-Step Solution:

1. **Understanding Rh Factor**: The Rh factor is a protein that can be present on the surface of red blood cells (RBCs). Individuals with this protein are classified as Rh-positive, while those without it are Rh-negative.

2. **Identifying the Parents' Rh Status**: In this scenario, the male is Rh-positive and the female is Rh-negative. This means that the mother does not have the Rh antigen.

3. **First Pregnancy**: During the first pregnancy, if the baby inherits the Rh-positive trait from the father, the baby will be Rh-positive. At the time of delivery, some of the baby's blood may mix with the mother's blood.

4. **Formation of Rh Antibodies**: When the Rh-positive blood from the baby enters the Rh-negative mother’s circulation, her immune system recognizes the Rh antigen as foreign and starts producing antibodies against it (anti-Rh antibodies).

5. **Second Pregnancy**: In the second pregnancy, if the fetus is again Rh-positive, the mother's pre-formed anti-Rh antibodies can cross the placenta and enter the fetal circulation.

6. **Destruction of Fetal RBCs**: The anti-Rh antibodies will attack the Rh-positive red blood cells of the fetus, leading to hemolysis (destruction of red blood cells), which can cause anemia in the fetus.

7. **Condition Name**: This condition is known as erythroblastosis fetalis or hemolytic disease of the newborn.

8. **Preventive Measures**: To prevent this condition in future pregnancies, Rh-negative mothers are often given an injection of Rh immunoglobulin (RhoGAM) after the first delivery to prevent the formation of Rh antibodies.

### Conclusion:
During the second pregnancy of an Rh-positive male and an Rh-negative female, the observed events would include Rh incompatibility and erythroblastosis fetalis due to the mother's immune response against the Rh-positive fetal blood cells.

### Answer:
The correct answer is option 4: both A (Rh incompatibility) and B (erythroblastosis).