Hemolytic disease of the fetus and newborn (HDFN) is a pregnancy condition in which the mother develops antibodies that attack the red blood cells of the fetus. Without medical intervention, this can cause the fetus to lack the necessary amount of red blood cells for optimal health and growth, resulting in anemia.
Because HDFN can pose risks to both the mother and child, an early diagnosis is key to allowing doctors to start the necessary treatments as quickly as possible.
First trimester and earlier
One of the ways doctors can identify a pregnancy that is highly at risk of HDFN is if the patient has experienced HDFN in a prior pregnancy. A previous pregnancy affected by HDFN raises the likelihood that subsequent pregnancies will be affected too, potentially even more severely than before.
Read more about HDFN testing and diagnosis
If the patient does not have a previous pregnancy affected by HDFN, doctors still have a way to detect the potential risk of HDFN as early as possible. This is the indirect Coombs test, which is performed during the first trimester and can identify maternal alloantibodies that are associated with HDFN. S
hould these antibodies be detected, your doctor will monitor their levels or titers. The higher the levels of these alloantibodies are in your body, the higher the risk of HDFN.
Second trimester and after
If you somehow missed out on an antibody screening during the first trimester, there is another way by which doctors typically detect the risk of HDFN. Remember that the effect of HDFN is fetal anemia, or a lack of red blood cells/hemoglobin. This can be detected via Doppler ultrasound, which is typically performed between 16 and 20 weeks of gestation. This ultrasound can be used to measure what is known as the middle cerebral artery peak systolic velocity (MCA-PSV). If this is elevated above a certain threshold, it signals to doctors that fetal anemia is present, which may lead to a diagnosis of HDFN, given that it is the most common cause of this condition.
Alternatively, doctors can use fetal blood sampling to check fetal hemoglobin levels. This procedure can be conducted as early as 18 weeks of gestation. However, because this procedure is invasive in that it requires direct access to the fetus via a specialized needle, there are considerable risks involved and are only used in severe cases when indicated.
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