Hemolytic disease of the newborn occurs when __________.ANSWERthe father is Rh+ and the mother is Rh–the mother is Rh+ and her fetus is Rh–both the parents are Rh–the father is Rh- and the mother is Rh+

Hemolytic disease of the newborn occurs when the father is Rh+ and the mother is Rh-.

Here's a step-by-step explanation:

1. Hemolytic disease of the newborn (HDN), also known as Rh disease, is a condition that occurs when a mother has Rh-negative blood and the baby in her womb has Rh-positive blood.

2. The Rh factor is a type of protein on the surface of red blood cells. Most people are Rh-positive, which means they have this protein. However, about 15% of the white population and 7% of the African-American population are Rh-negative, which means they lack this protein.

3. If the mother is Rh-negative and the father is Rh-positive, there's a chance that their baby could end up with Rh-positive blood. This can happen if at least one of the father's alleles is dominant.

4. During pregnancy, the mother's and baby's blood do not normally mix. However, during labor and delivery, or due to certain complications, the mother's and baby's blood can come into contact.

5. If the mother is Rh-negative and she's exposed to Rh-positive blood, her body may recognize the Rh factor as a foreign substance and start producing antibodies against it. This is known as Rh sensitization.

6. If the mother becomes pregnant again with an Rh-positive baby, her antibodies can cross the placenta and attack the baby's red blood cells. This can lead to HDN, which can cause serious illness, brain damage, or even death in newborns.

7. Therefore, HDN occurs when the father is Rh+ and the mother is Rh-.