Hemolytic Disease of the Newborn (HDN): A Blood Incompatibility Disorder
Hemolytic Disease of the Newborn (HDN), also called Erythroblastosis Fetalis, is a serious blood disorder in newborns that occurs when a mother’s immune system attacks the baby’s red blood cells. This happens due to blood type incompatibility, most commonly when an Rh-negative mother carries an Rh-positive baby. The mother’s immune system produces antibodies that destroy the baby’s red blood cells, leading to anemia, jaundice, and severe complications if untreated.
Explanation of HDN & How It Develops
1️⃣ Blood Type Incompatibility – The mother and baby have different Rh factors or incompatible ABO blood types.
2️⃣ Fetal Blood Enters the Mother’s Circulation – This can happen during pregnancy, delivery, miscarriage, or medical procedures.
3️⃣ Mother’s Immune System Reacts – If the mother is Rh-negative and the baby is Rh-positive, the mother’s immune system produces antibodies (Anti-D) against Rh-positive red blood cells.
4️⃣ Antibodies Attack the Baby’s Red Blood Cells – In a future pregnancy, these antibodies cross the placenta, destroying fetal red blood cells and causing HDN.
✔ HDN is most commonly caused by Rh incompatibility, but it can also occur with ABO blood group mismatches (less severe).
✔ The first pregnancy is usually unaffected, but subsequent pregnancies are at high risk without medical intervention.
Symptoms of Hemolytic Disease of the Newborn
| Mild HDN Symptoms | Severe HDN Symptoms |
|---|---|
| Jaundice (yellow skin & eyes) | Severe anemia (low red blood cell count) |
| Mild swelling | Rapid heart rate & breathing issues |
| Pale skin (low oxygen levels) | Enlarged liver or spleen |
| Lethargy or difficulty feeding | Brain damage due to bilirubin buildup (kernicterus) |
✔ Jaundice is an early sign of HDN due to excess bilirubin, a byproduct of red blood cell breakdown.
✔ Severe cases can be life-threatening without prompt medical treatment.
Risk Factors for Developing HDN
| Risk Factor | Why It Matters |
|---|---|
| Rh-negative mother, Rh-positive father | Increases risk of Rh incompatibility. |
| Previous pregnancy or miscarriage | The mother may have developed antibodies already. |
| No RhoGAM Injection | Without RhoGAM, the mother’s immune system can become sensitized. |
| Blood transfusion mismatch | Exposure to Rh-positive blood can trigger antibody formation. |
✔ Mothers with Rh-negative blood are tested early in pregnancy to determine if they have anti-Rh antibodies.
✔ RhoGAM injections prevent HDN by stopping the mother’s immune system from attacking fetal red blood cells.
How HDN Is Diagnosed
✔ Blood Tests for the Mother: Checks for Rh factor and anti-Rh antibodies.
✔ Ultrasound & Amniocentesis: Detects signs of fetal anemia or distress.
✔ Newborn Testing: Measures bilirubin levels and red blood cell count.
Treatment Options for HDN
| Treatment | Purpose |
|---|---|
| RhoGAM Injection (Prevention) | Given to Rh-negative mothers at 28 weeks and within 72 hours after delivery to prevent future HDN. |
| Phototherapy (Light Therapy) | Helps break down bilirubin in mild cases of HDN. |
| Blood Transfusions for Baby | In severe cases, an exchange transfusion replaces damaged red blood cells. |
| IV Immunoglobulin (IVIG) | Reduces immune response and prevents further breakdown of red blood cells. |
✔ Prevention with RhoGAM is the best approach, ensuring HDN does not develop in future pregnancies.
✔ Severe cases may require immediate medical intervention after birth.
Final Takeaway
Hemolytic Disease of the Newborn (HDN) occurs when a mother’s immune system attacks the baby’s red blood cells, leading to jaundice, anemia, and severe complications. It is most commonly caused by Rh incompatibility (Rh-negative mother, Rh-positive baby). Preventive measures like RhoGAM injections can stop HDN from developing, ensuring healthy pregnancies and newborns.