Rh incompatibility
Rh-induced hemolytic disease of the newborn; Erythroblastosis fetalis
Rh incompatibility is a condition that develops when a pregnant woman has Rh-negative blood and the baby in her womb has Rh-positive blood.
Antibodies from an Rh negative mother may enter the blood stream of her unborn Rh positive infant, damaging the red blood cells (RBCs). The infant responds by increasing RBC production and sending out immature RBCs that still have nuclei. This photograph shows normal RBCs, damaged RBCs, and immature RBCs that still contain nuclei.
Newborn jaundice (producing yellow skin) can have many causes, but the majority of these infants have a condition called physiological jaundice, a natural occurrence in the newborn due to the immature liver. This type of jaundice is short term, generally lasting only a few days. Jaundice should be evaluated by a physician until decreasing or normal levels of bilirubin are measured in the blood.
Antigens are large molecules (usually proteins) on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, drugs, and foreign particles. The immune system recognizes antigens and produces antibodies that destroy substances containing antigens.
Using bili lights is a therapeutic procedure performed on newborn or premature infants to reduce elevated levels of bilirubin. If blood levels of bilirubin become too high, the bilirubin begins to dissolve in the body tissues, producing the characteristic yellow eyes and skin of jaundice. Bilirubin also has an affinity for brain tissue, where it can accumulate and cause permanent brain damage.
Rh incompatibility occurs when the mother's blood type is Rh negative and her fetus' blood type is Rh positive.
Causes
During pregnancy, red blood cells from the unborn baby can cross into the mother's blood through the placenta.
If the mother is Rh-negative, her immune system treats Rh-positive fetal cells as if they were a foreign substance. The mother's body makes antibodies against the fetal blood cells. These antibodies may cross back through the placenta into the developing baby. They destroy the baby's circulating red blood cells.
When red blood cells are broken down, they make bilirubin. This causes an infant to become yellow (jaundiced). The level of bilirubin in the infant's blood may range from mild to dangerously high.
Firstborn infants are often not affected unless the mother had past miscarriages or abortions. This would sensitize her immune system. This is because it takes time for the mother to develop antibodies. All children she has later who are also Rh-positive may be affected.
Rh incompatibility develops only when the mother is Rh-negative and the infant is Rh-positive. This problem has become less common in places that provide good prenatal care. This is because special immune globulins called RhoGAM are routinely used.
Symptoms
Rh incompatibility can cause symptoms ranging from very mild to deadly. In its mildest form, Rh incompatibility causes the destruction of red blood cells. There are no other effects.
After birth, the infant may have:
- Yellowing of the skin and whites of the eyes (jaundice)
- Low muscle tone (hypotonia) and lethargy
Exams and Tests
Before delivery, the mother may have more amniotic fluid around her unborn baby (polyhydramnios).
There may be:
- A positive direct Coombs test result
- Higher-than-normal levels of bilirubin in the baby's umbilical cord blood
- Signs of red blood cell destruction in the infant's blood
Treatment
Rh incompatibility can be prevented with the use of RhoGAM. Therefore, prevention remains the best treatment. Treatment of an infant who is already affected depends on the severity of the condition.
Infants with mild Rh incompatibility may be treated with phototherapy using bilirubin lights. IV immune globulin may also be used. For infants severely affected, an exchange transfusion of blood may be needed. This is to decrease the levels of bilirubin in the blood.
Outlook (Prognosis)
Full recovery is expected for mild Rh incompatibility.
Possible Complications
Complications may include:
- Brain damage due to high levels of bilirubin (kernicterus)
- Fluid buildup and swelling in the baby (hydrops fetalis)
- Problems with mental function, movement, hearing, speech, and seizures
When to Contact a Medical Professional
Contact your health care provider if you think or know you are pregnant and have not yet seen a provider.
Prevention
Rh incompatibility is almost completely preventable. Rh-negative mothers should be followed closely by their providers during pregnancy.
Special immune globulins, called RhoGAM, are now used to prevent RH incompatibility in mothers who are Rh-negative.
If the father of the infant is Rh-positive or if his blood type is not known, the mother is given an injection of RhoGAM during the second trimester. If the baby is Rh-positive, the mother will get a second injection within a few days after delivery.
These injections prevent the development of antibodies against Rh-positive blood. However, women with Rh-negative blood type must get injections:
- During every pregnancy
- After a miscarriage or abortion
- After prenatal tests such as amniocentesis and chorionic villus biopsy
- After injury to the abdomen during pregnancy
References
Kaplan M, Wong RJ, Burgis JC, Sibley E, Stevenson DK. Neonatal jaundice and liver diseases. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 91.
Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM. Blood disorders. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 124.
Moise KJ. Red cell alloimmunization. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 40.
Version Info
Last reviewed on: 1/24/2023
Reviewed by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
