Question

Explain what occurs in hemolytic disease of the newborn. (pages $127-29$ )

Short answer

Hemolytic Disease of the Newborn (HDN), also known as erythroblastosis fetalis, is a blood-related disorder that occurs in a fetus or newborn infant when there is an incompatibility between the blood types of the mother and the baby. This condition is most commonly caused by an Rh-negative mother having an Rh-positive baby. The maternal antibodies can cross into the baby's bloodstream and attack the baby's red blood cells, leading to symptoms such as jaundice, anemia, heart failure, and swelling of the body. HDN can be life-threatening if left untreated. Prevention of the disease involves administering Rh immunoglobulin to the Rh-negative mother during pregnancy and after childbirth if the baby is Rh-positive, while treatment may involve blood transfusions for the baby.

Step-by-step solution

Understanding the basic concept of Hemolytic Disease of the Newborn

HDN is also known as erythroblastosis fetalis. It's a blood-related disorder that occurs in a fetus or newborn infant. In this condition, the red cells of the baby are destroyed by the antibodies of the mother caused by blood group incompatibility.

Identifying the cause of Hemolytic Disease of the Newborn

HDN most commonly occurs when a mother with an Rh-negative blood type has a baby with an Rh-positive blood type. A Rh-negative mother hasn’t any Rh antigen, while the Rh-positive baby does. If the maternal antibodies to Rh-positive blood cells pass into the fetal bloodstream, they can destroy the baby's red blood cells, causing HDN.

Understanding the process of Hemolytic Disease of the Newborn

During childbirth, when the blood of the mother and baby may mix, the mother's body may react as if it were allergic to the baby's Rh-positive cells and produce antibodies against them. These antibodies could then potentially cross into the baby's bloodstream and attack the baby's red cells. However, it's more likely to occur in second or subsequent pregnancies with an Rh-positive baby because the mother's body has already produced the antibodies during the first exposure.

Understanding the symptoms and consequences of HDN

If the baby's red blood cells are being destroyed, the baby can become very unwell, with symptoms including: jaundice, anemia, heart failure, and swelling of the body. Without treatment, HDN can be life threatening.

Understanding the prevention and treatment of HDN

The disease can be prevented by administering a medicine called Rh immunoglobulin to the Rh-negative mother during pregnancy and again after childbirth if the baby is Rh-positive. If the disease does occur, the baby might need treatment with blood transfusions, either before birth or after birth. Hence, Hemolytic Disease of the Newborn occurs due to blood type incompatibility between a mother and her fetus, causing the mother's immune system to attack the red blood cells of the baby, and can potentially be prevented with appropriate medical intervention.

Key concepts

Erythroblastosis Fetalis

Erythroblastosis fetalis, also known as hemolytic disease of the newborn (HDN), is a serious condition affecting newborns. It happens when the mother's immune system mistakenly attacks the red blood cells of the baby. This condition can lead to serious health problems for the newborn. Because the red blood cells are attacked, the baby can suffer from severe anemia. This means there are not enough healthy red blood cells to carry oxygen through the baby’s body. Without enough oxygen, the baby’s organs and tissues can't function properly. Symptoms of erythroblastosis fetalis in a newborn may include:

• Jaundice, which is yellowing of the skin and eyes
• Swelling under the skin (edema)
• An enlarged liver and spleen
• Difficulties in breathing

This condition demands immediate medical attention to prevent long-term issues or even fetal death.

Blood Group Incompatibility

Blood group incompatibility is the primary cause behind erythroblastosis fetalis. This arises when the blood type of the mother does not match the blood type of her baby. Among the diverse blood group systems, the Rh factor is the most commonly involved in such cases. The mismatch in blood groups leads to the mother's immune system treating the baby's blood cells as foreign invaders, prompting an immune response. To simplify, think of it as a mismatch warning from the body's defense system.

• A compatible blood group: No issues arise, as mother's body recognizes the baby's blood cells.
• Incompatibility scenario: Mother's body perceives threat, produces antibodies to destroy the perceived "enemy" cells.

The consequence of this misrecognition can be devastating for the fetus if not diagnosed and managed properly.

Rh-negative and Rh-positive Blood Type

The Rh factor is a crucial component of your blood, specifically found on red blood cells. It determines whether blood is Rh-negative or Rh-positive. Most people have Rh-positive blood, meaning they have the Rh protein present on their red blood cells. Rh-negative individuals lack this protein, which becomes significant during pregnancy if the mother is Rh-negative and the baby is Rh-positive.
When an Rh-negative mother is pregnant with an Rh-positive baby, it sets the stage for potential conflict between the maternal and fetal blood types. The mother’s immune system might see the baby’s Rh-positive blood as a threat and create antibodies against it.
Such a situation is far more likely to cause trouble in subsequent pregnancies, as the mother's body has built a memory of the foreign Rh-positive cells and responds more aggressively upon repeated exposure.

Maternal Antibodies

Maternal antibodies play a pivotal role in erythroblastosis fetalis. These are proteins generated by the mother's immune system intending to protect her body from "non-self" entities or threats. When there is blood group incompatibility, particularly Rh incompatibility, the mother’s immune system believes the Rh-positive cells from the fetus are foreign. It will produce antibodies against them. These antibodies can cross the placenta into the fetal bloodstream. Once in the fetus, these maternal antibodies attack the red blood cells of the baby, breaking them down, which leads to serious complications. This immune attack may lead to symptoms such as anemia and jaundice in the newborn, requiring close monitoring and possible interventions.

Rh Immunoglobulin

Rh immunoglobulin is a preventive treatment designed to tackle the issue of Rh incompatibility. It’s given to Rh-negative mothers during and after pregnancy to avert the development of harmful antibodies against Rh-positive fetal blood cells. The administration of Rh immunoglobulin acts as a type of vaccination for the mother’s immune system. Instead of producing long-term antibodies that can attack a Rh-positive baby, this medication prevents the immune system from recognizing the Rh-positive cells as a threat.

• Administered during the 28th week of pregnancy
• Also given within 72 hours post-delivery if the newborn is Rh-positive
• Effectively keeps the pregnancy safe by preventing antibody formation

Through this intervention, the risk of developing erythroblastosis fetalis in subsequent pregnancies is significantly reduced, ensuring better health outcomes for the newborn.