Rh Disease
Rh blood-type mismatch between mother and baby
Quick Facts
- Type: Newborn hemolytic condition
- Cause: Rh-negative mother, Rh-positive baby
- Key prevention: Rh immune globulin (anti-D) injection
- Risk: Often higher in later pregnancies
Overview
Rh disease, also called Rh incompatibility or hemolytic disease of the newborn, occurs when a pregnant woman who is Rh-negative carries a baby who is Rh-positive. The Rh factor is a protein on the surface of red blood cells; people who have it are Rh-positive and those who lack it are Rh-negative. If Rh-positive blood from the baby enters the mother's circulation, her immune system may treat it as foreign and make antibodies against it.
These antibodies can cross the placenta and attack the red blood cells of an Rh-positive baby, leading to anemia and jaundice. A first pregnancy is often unaffected because sensitization usually happens during or after that pregnancy; later Rh-positive pregnancies carry more risk. Thanks to a preventive injection, severe Rh disease is now uncommon where prenatal care is available.
Symptoms
The mother has no symptoms from Rh sensitization itself. The effects appear in the baby and can range from mild to serious:
- Jaundice, often appearing soon after birth as bilirubin builds up
- Anemia, sometimes with pale skin and a fast heart rate
- Enlargement of the liver or spleen
- In severe, untreated cases, widespread swelling and fluid buildup in the baby (a serious condition called hydrops)
The severity depends on how much antibody is present and how strongly it attacks the baby's red cells. Modern prenatal monitoring detects problems early so treatment can begin before birth if needed.
Causes
Rh disease develops in two stages: sensitization, then attack on a later baby's red cells.
- Exposure: an Rh-negative mother's blood mixes with Rh-positive fetal blood, which can happen during delivery, miscarriage, bleeding in pregnancy, certain procedures, or trauma.
- Sensitization: the mother's immune system makes anti-Rh (anti-D) antibodies.
- Attack: in a later Rh-positive pregnancy, these antibodies cross the placenta and destroy the baby's red blood cells.
Because sensitization usually occurs during a first pregnancy or delivery, the first Rh-positive baby is often unaffected while later ones are at higher risk if no preventive treatment is given.
Risk Factors
- An Rh-negative mother carrying an Rh-positive baby (father is Rh-positive)
- A previous Rh-positive pregnancy without preventive treatment
- Previous miscarriage, abortion, or ectopic pregnancy with Rh-positive blood exposure
- Bleeding during pregnancy or abdominal trauma
- Certain procedures such as amniocentesis
Diagnosis
Rh disease is detected through routine prenatal testing and monitoring.
- Blood typing: the mother's ABO and Rh type are checked early in pregnancy.
- Antibody screen: tests for anti-Rh antibodies in the mother's blood.
- Fetal monitoring: if sensitization is present, ultrasound and Doppler measurements can detect signs of fetal anemia, and amniocentesis may be used.
- Newborn testing: after birth, the baby's blood type, bilirubin level, and a direct antibody (Coombs) test help assess the condition.
Treatment
Treatment depends on whether sensitization has occurred and how the baby is affected.
- Prevention with Rh immune globulin: for non-sensitized Rh-negative mothers, an injection of Rh immune globulin (anti-D) during pregnancy and after delivery prevents sensitization. This is the cornerstone of care.
- Monitoring an affected pregnancy: close ultrasound and blood-flow checks to watch for fetal anemia.
- Intrauterine transfusion: in severe cases, a blood transfusion can be given to the baby before birth.
- Newborn treatment: phototherapy for jaundice and, rarely, an exchange transfusion for very high bilirubin or severe anemia.
With modern prevention and monitoring, most pregnancies have good outcomes.
Prevention
Rh disease is largely preventable with proper prenatal care:
- Have your blood type and Rh status checked early in pregnancy
- If you are Rh-negative, receive Rh immune globulin (anti-D) as recommended, typically around the 28th week and again shortly after delivery of an Rh-positive baby
- Receive Rh immune globulin after any event that may mix fetal and maternal blood, such as miscarriage, bleeding, trauma, or certain procedures
- Attend all prenatal appointments so antibody levels can be monitored
When to See a Doctor
If you are pregnant or planning pregnancy, see your healthcare provider early so your Rh status can be checked and preventive treatment arranged if you are Rh-negative. Seek prompt medical care during pregnancy if you have:
- Vaginal bleeding or abdominal trauma, which may require Rh immune globulin
- Decreased fetal movement
After birth, a newborn with worsening jaundice, deep yellow coloring, poor feeding, or unusual sleepiness should be evaluated promptly, as these can signal rising bilirubin that needs treatment.
Frequently Asked Questions
Can Rh disease be prevented?
Yes, in most cases. Rh-negative mothers can receive Rh immune globulin (anti-D) during pregnancy and after delivery, which prevents the immune system from making antibodies. This has made severe Rh disease uncommon where prenatal care is available.
Why is the first pregnancy usually not affected?
Sensitization, when the mother's immune system makes anti-Rh antibodies, usually happens during or after the first Rh-positive pregnancy. The antibodies are then present for later pregnancies, so subsequent Rh-positive babies are at higher risk if no preventive treatment was given.
What happens if Rh disease is not treated?
Untreated, the mother's antibodies can destroy the baby's red blood cells, causing anemia and jaundice that may become severe and, in serious cases, lead to dangerous swelling and fluid buildup. Modern monitoring and prevention make these outcomes rare.
Does Rh immune globulin help if I am already sensitized?
No. Rh immune globulin prevents sensitization but does not reverse it once antibodies have formed. If you are already sensitized, the focus shifts to monitoring the pregnancy closely and treating the baby as needed.
Is Rh disease the same as ABO incompatibility?
Both involve maternal antibodies attacking a baby's red blood cells, but they involve different blood factors. Rh disease relates to the Rh protein and often worsens in later pregnancies, while ABO incompatibility involves the ABO blood groups and is usually milder.
References
- MedlinePlus, U.S. National Library of Medicine. Rh incompatibility.
- Mayo Clinic. Rh factor blood test.
- American College of Obstetricians and Gynecologists (ACOG). The Rh factor.
- National Institutes of Health (NIH). Hemolytic disease of the newborn.