Which of the following situation will be fatal to second foetus ?

Options

A. If `Rh^(+)` man marries `Rh^(+)` woman
B. If `Rh^(-)` man marries `Rh^(+)` woman
C. If `Rh^(+)` man marries `Rh^(-)` woman
D. If `Rh^(-)` man marries `Rh^(-)` woman

Answer

To determine which situation could be fatal to the second fetus, we need to understand the implications of the Rh factor in pregnancy. Here’s a step-by-step breakdown:

### Step 1: Understand the Rh Factor
The Rh factor is a protein that can be present on the surface of red blood cells. Individuals with this protein are considered Rh positive (Rh+), while those without it are Rh negative (Rh-).

**Hint:** Remember that the Rh factor is crucial in determining blood compatibility between a mother and her fetus.

### Step 2: Identify the Scenarios
The question presents different scenarios involving an Rh positive man and an Rh negative woman. We need to analyze how these combinations affect the first and second pregnancies.

**Hint:** Look for combinations of Rh factors in the parents and how they might affect the fetus.

### Step 3: First Pregnancy Considerations
In the first pregnancy, if the Rh negative mother carries an Rh positive fetus (inherited from the Rh positive father), the mother may not have any issues initially. However, during childbirth, some of the Rh positive blood from the fetus can enter the mother's bloodstream, prompting her immune system to produce antibodies against the Rh factor.

**Hint:** The first pregnancy often does not have complications, but it sets the stage for potential issues in subsequent pregnancies.

### Step 4: Second Pregnancy Complications
In the second pregnancy, if the mother is again carrying an Rh positive fetus, her immune system, now sensitized from the first pregnancy, can attack the fetal red blood cells. This condition is known as hemolytic disease of the newborn (HDN) and can be life-threatening for the fetus.

**Hint:** Consider how the mother's immune response changes after the first pregnancy.

### Step 5: Conclusion
The situation that would be fatal to the second fetus is when the mother is Rh negative and the father is Rh positive, leading to the possibility of the second fetus being Rh positive as well. This results in the mother’s immune system attacking the fetus due to the Rh incompatibility.

**Final Answer:** The situation that will be fatal to the second fetus is when the mother is Rh negative and the father is Rh positive (option C).

### Summary of Steps:
1. Understand the Rh factor and its significance.
2. Analyze the scenarios involving Rh positive and Rh negative parents.
3. Recognize that the first pregnancy may not have complications but sensitizes the mother.
4. Identify that the second pregnancy can be fatal if the fetus is Rh positive.
5. Conclude that the answer is when the mother is Rh negative and the father is Rh positive.