If a woman who has developed anti-Rh antibodies becomes pregnant with a second Rh+ fetus, the antibodies in her blood may pass through the placenta and react with the red blood cells of the fetus

If a woman who has developed anti-Rh antibodies becomes pregnant with a second Rh+ fetus, the antibodies in her blood may pass through the placenta and react with the red blood cells of the fetus. The fetus then develops a condition called

A hereditary hemochromatosis

B hemophilia

C erythrocytosis

D erythroblastosis fetalis

The correct answer and explanation is:

The correct answer is:

D. erythroblastosis fetalis

Explanation:

Erythroblastosis fetalis, also known as hemolytic disease of the newborn (HDN), is a condition that occurs when a Rh-negative mother has developed anti-Rh antibodies (sensitization) and is pregnant with a second or subsequent fetus that is Rh-positive.

Here’s how it happens:

1. First Pregnancy Sensitization
   During the first pregnancy with an Rh-positive fetus, small amounts of the fetal red blood cells can enter the maternal circulation, especially at delivery or if there is bleeding. Because the mother is Rh-negative and the fetus is Rh-positive, her immune system recognizes the Rh antigen on fetal red blood cells as foreign and begins producing anti-Rh antibodies.
2. Antibody Formation
   These antibodies (IgG type) remain in the mother’s bloodstream after the first pregnancy. They usually do not affect the first fetus significantly because sensitization mostly happens at delivery.
3. Second Pregnancy Risk
   In a subsequent pregnancy with another Rh-positive fetus, the mother’s anti-Rh antibodies can cross the placenta and enter the fetal circulation.
4. Fetal Red Blood Cell Destruction
   Once in the fetal bloodstream, these maternal antibodies attach to the Rh antigens on the fetal red blood cells and cause their destruction (hemolysis).
5. Consequences for the Fetus
   The destruction of red blood cells leads to fetal anemia, and the fetal bone marrow tries to compensate by producing many immature red blood cells called erythroblasts, which can be seen in the fetal blood (hence “erythroblastosis”). Severe anemia can cause heart failure, hydrops fetalis (generalized swelling), and even fetal death if untreated.

Why the other options are incorrect:

• A. Hereditary hemochromatosis
  This is a genetic disorder causing excessive iron absorption and storage in the body, unrelated to Rh incompatibility or pregnancy.
• B. Hemophilia
  Hemophilia is a genetic bleeding disorder caused by deficiency of clotting factors, not related to maternal-fetal blood group incompatibility.
• C. Erythrocytosis
  This refers to an increased number of red blood cells, which is the opposite of what occurs in erythroblastosis fetalis, where there is destruction and anemia.

Summary:

Erythroblastosis fetalis is a serious immune-related condition caused by Rh incompatibility between an Rh-negative mother and an Rh-positive fetus in subsequent pregnancies. It is characterized by the destruction of fetal red blood cells by maternal anti-Rh antibodies, leading to anemia and potential fetal complications. This condition is preventable with Rh immunoglobulin administration to the mother after the first pregnancy or any event causing fetal-maternal blood mixing.