Red Blood Cell Antibodies in Pregnancy
A blood test found an antibody in your blood. Antibodies are made by your body's defense system.
Some antibodies can stick to a baby's red blood cells and cause anemia. Anemia means the baby does not have enough red blood cells.
Many antibodies do not harm the baby. Your care team will find out which antibody you have and whether your baby needs more testing.
What happens next?
- the lab will identify the antibody
- a blood test may measure how much antibody is present; this is called a titer
- tell your care team about prior pregnancy loss, blood transfusion, or a baby with anemia or severe jaundice
- testing may be used to find out if the baby has the matching marker
What if the baby is at risk?
You may need more blood tests and ultrasounds.
A middle cerebral artery (MCA) Doppler checks blood flow in a small artery in the baby's brain. Blood that moves too fast may be a sign of anemia.
If the baby does not have the matching marker, that antibody cannot harm the baby.
Can anemia be treated?
Yes. If the baby may have severe anemia, you will be sent to a special baby care center.
The team may test a small sample of the baby's blood. A baby with severe anemia may need a blood transfusion before birth. In some cases, delivery may be safer.
What may happen after birth?
Your baby may need blood tests.
Some babies need light treatment for yellow skin, called jaundice.
A few babies need a blood transfusion. Your baby's doctor will make a care plan before birth.
How can the baby's marker be checked?
A blood test from you may sometimes show the baby's marker.
A blood test from the baby's father may also help. At times, your doctor may offer amniocentesis.
What should I remember?
Not every red blood cell antibody causes a problem.
Your care plan depends on the type and amount of antibody, whether the baby has the matching marker, and whether there was a prior affected pregnancy.
Medical references used for this handout
- Society for Maternal-Fetal Medicine. Clinical Guideline #8: The fetus at risk for anemia: diagnosis and management. Am J Obstet Gynecol. 2015;212:697-710. Reaffirmed 2025.
- American College of Obstetricians and Gynecologists. Practice Bulletin No. 192: Management of Alloimmunization During Pregnancy. Obstet Gynecol. 2018;131:e82-e90.
- Moise KJ Jr, Markham KB, Spinella PC, et al. A Clinical Practice Guideline for the Management of Pregnancy Alloimmunized to Red Blood Cell Antigens. JAMA Netw Open. 2025;8:e2544649.