A Patient's Introduction to Alloimmunization and HDFN.

Welcome! Being diagnosed with antibodies can be overwhelming and stressful, especially right after learning about your diagnosis. The first thing you should know is that there is hope for your baby and the survival rate is very high with the right monitoring and treatment. If you have been told that you are positive for a red cell antibody such as anti-D, Kell, C, c, E, e, etc. it means that you have maternal alloimmunization. This happened because you were exposed to a blood type different from your own, either through a pregnancy or a blood transfusion. During pregnancy, these antibodies could go through the placenta and affect your unborn baby. When that happens it is called Hemolytic Disease of the Fetus and Newborn (HDFN). If you are unsure of what a word means, please view our glossary for additional definitions and abbreviations.

What are antibodies?

Everyone has antibodies in their blood. Antibodies keep you healthy by finding viruses and bacteria in your body and attacking them to help keep you from getting sick.

Having maternal alloimmunization is rare. It means that you make red blood cell antibodies. Your body has made antibodies that look for red blood cells that they think should not be there, even though these red blood cells are not dangerous to you like a virus or bacteria. If you have anti-D antibodies, for example, this means that your antibodies look for blood cells that have the D antigen on them. They will attack blood cells that have the D antigen.

When you become pregnant, you and your baby share blood through your placenta. Your baby may have the D antigen on his blood cells. If he does, your D antibodies may attack your baby’s red blood cells. If your baby does not have enough red blood cells, he or she becomes anemic.

What are the risks?

The only risk to you personally is if you receive a blood transfusion. If you get the wrong blood during a blood transfusion you are 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 go through 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, 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, or for thrombocytopenia. Thankfully there are treatments that can be used to protect your baby from these risks.

How can I protect my baby?

The best way to protect your baby is to find a good Maternal Fetal Medicine Specialist (perinatologist) who is knowledgeable about these antibodies. You should ask to be sent to an MFM doctor if you do not already have an MFM. You can also protect your baby by educating yourself about alloimmunization and HDFN. You need to make sure that you get the proper prenatal tests, monitoring, and treatment.

Plasmapheresis and IVIG treatments may be an option for you beginning early in your pregnancy to protect the baby until he or she is big enough for an intrauterine transfusion (IUT). Talk with your doctor about these options if you have had a previous loss because of your antibodies, or a severely affected baby, or if you have a very high titer early in pregnancy (>256).

What monitoring and treatment should I have during pregnancy?

When you are diagnosed with antibodies you will have blood drawn every 4 weeks until 28 weeks, then every 2 weeks, to see the amount, or titer, of antibodies in your blood. If your titer (or quant in the UK) goes above the critical level (4 for Kell, 16 for others), then you will have weekly MCA scans instead. An MCA scan is a special ultrasound of the baby's brain to check for anemia. If your results from the MCA scan show anemia, then your doctor will prepare you for an IUT. During an IUT, an experienced MFM doctor puts a needle through your belly in order to send blood to your baby. You will also have weekly non-stress tests from 32 weeks until you deliver.

The father should have his blood drawn to look at his antigen phenotype. This will tell you and your doctor if your baby could have the antigen, or blood type, that your antibodies may destroy. CffDNA testing is available to find out if a baby is at risk or safe from anti-Kell, anti-D, anti-C, anti-c, anti-E, and anti-e. You can ask your doctor if it is an option for you. If cffDNA testing is not currently available in your country, you have the option to ship the blood to a different country for testing.

Read more about prental testing and treatment.

When should I deliver my baby? Do I need a c-section?

Women with antibodies usually give birth between 35 and 38 weeks, but the time of delivery depends on your specific situation and what is safest for your baby. Even if titers are low, the majority of alloimmunized women are induced early. Having antibodies does not automatically mean you must have a c-section.

What treatment and monitoring does the baby need after birth?

After birth, the baby’s disease is called Hemolytic Disease of the Newborn (HDFN). After birth, the baby should have a Direct Agglutination Test (DAT, also called a direct Coombs Test) run. If the baby’s DAT is positive, or if the baby is antigen positive, then he or she needs to be monitored for signs of HDFN. Baby will also need to have his bilirubin, hemoglobin, reticulocyte, neutrophil count, and thrombocyte count tested regularly. High bilirubin can be treated with phototherapy, IVIG, and exchange transfusions. Anemia can be treated with blood transfusions. Iron should not be given to your baby unless your baby’s ferritin level is checked first. Giving iron to babies with HDFN without testing the ferritin levels first can be dangerous. Always get a ferritin test before giving iron.

Babies with HDFN are at risk for delayed onset anemia for up to 12 weeks after birth, so your baby should have weekly blood tests until hemoglobin or hematocrit is going up steadily on its own without a blood transfusion. Once this happens, your baby is safe and no longer has HDFN.

Read more about what to expect after birth, infant testing, treatment options, and what the long-term outcomes are for babies with HDFN.

Can I have more children?

You will always have antibodies, even when you are not pregnant or when your titer is very low. However, your antibodies do not have to limit your family size. If you want to learn more about how to prepare for another alloimmunized pregnancy, talk to your doctor before you get pregnant again. You can also read our page about ways to grow your family.