Hemolytic disease of the fetus and newborn (HDFN) occurs when a mismatch is reported between a mother’s and her baby’s blood type (A, B, AB, or O) or Rhesus (Rh) factor (Rh-positive or Rh-negative) during pregnancy. HDFN can be associated with major health issues and even death, so prompt recognition and treatment of the disorder are critical.
HDFN is considered an immune-mediated red blood cell (RBC) disorder. In HDFN, maternal antibodies attack fetal or newborn RBCs, which can then break down quickly. The disease can strike when a pregnant woman develops antibodies against antigens on the fetal RBCs that have been inherited from the father. Numerous antibodies to RBC antigens can be linked to HDFN, such as those from the ABO, Rh and other blood group systems.
How HDFN can develop
Women can develop antibodies to RBC antigens because of a prior pregnancy or a blood transfusion. In such cases, the maternal antibodies may cross the placenta and then bind to the antigen on the fetal RBCs, which can lead to their destruction or the suppression of erythropoiesis in the fetal bone marrow.
How does HDFN present early on?
The breakdown or destruction of RBCs seen in HDFN is known as hemolysis. Earliest signs of hemolysis can include anemia and jaundice in the first few days to weeks of life.
Anemia
In infants with anemia, blood testing reveals a low number of RBCs. Severe anemia can be associated with life-threatening illness as it becomes more difficult for oxygen to be delivered throughout the body.
Jaundice
In newborns with jaundice, the blood contains an excessive amount of bilirubin—a yellow pigment made during the breakdown of RBCs. Babies with higher-than-normal blood levels of bilirubin develop a condition known as hyperbilirubinemia, in which yellow coloring is caused by a build-up of bilirubin in the skin.
In these infants, the skin and the whites of their eyes have a yellow discoloration. If left untreated, severe jaundice can be associated with hearing issues, deafness and brain damage.
Other signs of HDFN
HDFN can present with other early signs as well, including pale skin, very dark urine, increased tiredness or irritability, rapid breathing, rapid heart rate and poor feeding.
Diagnosis of HDFN
To check for the presence of HDFN, the following tests can be performed in a mother prior to her baby’s birth:
Blood tests
HDFN can be diagnosed by checking for the presence of maternal antibodies against RBCs with the following methods:
- Agglutination (the clumping of particles together) via an indirect antibody test.
- A positive direct antibody test (DAT) to detect the presence of antibodies against circulating RBCs in the body.
Determination of the father’s RBC antigen status
If a pregnant woman is found to have alloimmunization, which is an immune system response due to ABO or Rh incompatibility between the mother’s and the fetus’s blood, the next step is to determine the father’s RBC antigen status.
Ultrasound
High-resolution anatomy ultrasound can be used to check the fetus for any organ enlargement, which may indicate the presence of anemia
Amniocentesis
When amniocentesis is performed, a small amount of amniotic fluid is removed from the uterus and examined in the laboratory to identify the following:
- The presence of any genetic abnormalities
- The fetal blood type
- Fetal well-being, including any infections or other illnesses
- Infant lung maturity and development
Can HDFN be treated prior to a baby’s birth?
Depending on a mother’s condition, if her baby is diagnosed with HDFN prior to birth, some or all of the following tests and treatments may be recommended.
- Laboratory tests to measure the strength of the mother’s RBC antibodies.
- An ultrasound to check the flow of blood through the unborn baby’s veins.
- Intrauterine fetal transfusion of RBCs to provide the baby with new RBCs and thus prevent the development of anemia.
- Early delivery once a baby has gained sufficient weight, to prevent the worsening of HDFN.
