Munson Health
Rh Incompatibility and Isoimmunization

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by Alan R

(RhD Incompatibility)



A baby's Rh status is determined from the mother and father. If the mother is Rh negative and the father is Rh positive, the baby has at least a 50% chance of being Rh positive. However, Rh isoimmunization will only happen if the baby's Rh-positive blood enters the mother's blood flow. In most pregnancies, the mother's and baby's blood will not mix. The baby's blood may come into contact with the mother's blood flow during:
The mix in blood happens most often at the end of pregnancy. This means it is rarely a problem in a woman's first pregnancy. The mother's antibodies could affect a future pregnancy with a baby with Rh-positive blood even if the blood is not mixed.
A woman can also become sensitized to Rh-positive blood if she receives an incompatible blood transfusion .
Blood Flow to Fetus
Placenta Function
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Symptoms and complications will only affect the baby. The complications occur when standard preventive measures are not taken. The symptoms can vary from mild to severe.
Symptoms that can develop in the baby include:
A complication of untreated jaundice is kernicterus, a syndrome which can affect the baby's nervous system. Contact your doctor right away if your baby:
  • Has a yellow or orange appearance to the skin
  • Does not sleep
  • Is hard to wake up
  • Is not breastfeeding or has difficulty sucking from a bottle
  • Is restless or fussy
Call for emergency medical help if your baby has:
  • High pitched crying or crying that won't stop
  • A bowed body
  • A stiff, limp, or floppy body
  • Strange eye movements


Rh incompatibility is almost completely preventable using immunization. The best treatment is prevention.
If Rh incompatibility does occur, then the baby may need treatment based on symptoms such as:

Swelling of the Body (Hydrops fetalis)

More severe condition that may require:
  • Intrauterine fetal transfusion—to replace blood cells that are being destroyed during pregnancy
  • Early induction of labor
  • A direct transfusion of packed red blood cells which are compatible with the infant's blood
  • An exchange transfusion to remove the mother's antibodies
  • Control of congestive heart failure and fluid retention

Kernicterus may be treated with:

  • Exchange transfusion—replacing baby's blood with blood with Rh-negative blood cells
  • Phototherapy
Both hydrops fetalis and kernicterus are more severe conditions. Long-term problems can also develop with severe cases, including:


American Congress of Obstetricians and Gynecologists

American Pregnancy Association



Society of Obstetricians and Gynaecologists of Canada

Women's Health Matters



Hemolytic disease of the newborn. EBSCO DynaMed website. Available at: Updated February 7, 2014. Accessed March 18, 2014.

Jaundice and kernicterus. Centers for Disease Control and Prevention website. Available at: Updated June 27, 2013. Accessed March 18, 2014.

Rh factor. American Pregnancy Association website. Available at: Updated April 2006. Accessed March 18, 2014.


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