**Question:** A baby's blood group was determined as 0 Rh negative. Select the blood group, the baby's mother or father will not have: WB 07

**Core Concept:** Blood group system and Rh factor in humans.

Blood grouping is a process used to identify the antigens present on red blood cells, which determine an individual's blood group. Antigens are specific proteins or sugars that can elicit an immune response when foreign. In humans, there are several blood group systems, including the ABO system (A, B, AB, O) and the Rh (Rhesus) factor. The Rh factor is a protein found on the surface of red blood cells and is labeled as positive (Rh+ or D antigen) or negative (Rh- or no D antigen).

**Why the Correct Answer is Right:** In the case of an Rh-negative baby (0 Rh negative), the baby's parents must be either Rh-negative or have a Rh-positive parent with a Rh-negative baby. The mother or father cannot have an Rh-positive blood group because their blood would be Rh-positive, which is incompatible with the baby's Rh-negative blood group.

**Why Each Wrong Option is Incorrect:**

A. Blood group A: An Rh-negative baby cannot have a blood group A because the A antigen is present, making the parent with group A Rh positive.

B. Blood group B: An Rh-negative baby cannot have a blood group B for the same reason as option A, as the B antigen is present in blood group B, indicating Rh positivity.

C. Blood group AB: An Rh-negative baby cannot have blood group AB because the AB antigen is present, indicating Rh positivity in the parents.

D. Blood group O: An Rh-negative baby cannot have blood group O because the O antigen is present, indicating Rh positivity in the parent with group O.

**Clinical Pearl:** In cases where a Rh-negative mother marries a Rh-positive partner, the child may be Rh-negative. To prevent sensitization of the mother's immune system to the father's Rh antigen, immune globulin (Rh immunoglobulin) is administered to the mother during pregnancy and after childbirth if the father is Rh-positive and the baby is Rh-negative. This prophylactic intervention helps avoid a potentially dangerous immune response in the mother, which could lead to a condition called hemolytic disease of the newborn.

**Correct Answer:** The correct answer is not explicitly mentioned in the options provided, but considering the explanation above, the correct answer would be:

**Correct Answer: O Rh-negative**

In this scenario, the baby is Rh-negative due to the mother being Rh-negative. The father could have any blood group, including O Rh-positive, as the question suggests. If the father is Rh-positive, the mother will receive prophylactic immunoglobulin to prevent sensitization.