Maternal Alloimmunization and HDFN

A brief overview for newly diagnosed patients and their families

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What is red blood cell alloimmunization and how does it cause HDFN?

Maternal alloimmunization occurs when a woman makes red blood cell antibodies as a result of foreignblood mixing. These antibodies can cross theplacenta and attack the unborn child, a disease called hemolytic disease of the fetus and newborn(HDFN). HDFN can have devastating consequences including anemia, hyperbilirubinemia, and death.W ith close monitoring and timely treatment, babies with HDFN have a very high survival rate. Unfortunately, due to the rarity of alloimmunization and the variation in care practices around the world,well-managed pregnancies and ideal infanto utcomes are not universal - but they can be!

What causes maternal alloimmunization?

Most women find out that they have a red cellantibody, or maternal alloimmunization, when their first trimester antibody screen comes back positive. This often comes as a shock since the antibodies weren’t present/detected in the previous pregnancy. Our immune system creates antibodies when something foreign is detected in our bodies. The antibodies keep us safe by attacking the foreign thing (such as a virus) that is threatening us. This can happen when we are exposed to a blood type that is different from our own. Our body thinks the foreign blood is a threat, so our immune system creates antibodies specifically designed to destroy the different blood type. This exposure happens during pregnancy, childbirth or from a blood transfusion.

What are the risks?

Once your body has created antibodies you will have them for the rest of your life. They will not affect you or put you in danger unless you need a blood transfusion. The donor blood you are given must be matched to your specific antibodies or you could be at risk for a hemolytic transfusion reaction. It is important to tell your doctors about your antibodies for the rest of your life, and especially before a blood transfusion. The biggest risk is to your baby during pregnancy and after birth. Your antibodies can cross the placenta during pregnancy and destroy your baby’s red blood cells, causing the baby to become anemic. If fetal anemia is not treated properly during pregnancy, serious problems such as hydrops, organ damage, or death can occur. If HDFN is not treated properly after birth, serious problems such as anemia, high bilirubin, brain damage, or death can occur. Infants with HDFN are also at risk for neutropenia and thrombocytopenia. Thankfully there are treatments that can be used to protect your baby from these risks.

Monitoring and Treatment

An exact monitoring and treatment plan will vary, but in general women can expect: