Hemolytic disease of the fetus and newborn (HDFN) is a condition that occurs when a baby’s red blood cells (RBCs) break down quickly, which is called hemolysis. Certain tests can be performed during the antenatal period—the time before the baby’s birth—to check for the presence of HDFN.
Why does HDFN occur?
In HDFN, there is a mismatch between a mother’s and her baby’s blood type (A, B, AB, or O) and/or Rhesus (Rh) factor (positive or negative) during pregnancy. The passage of maternal antibodies through the placenta leads to immune hemolysis of fetal and neonatal RBCs. These can be naturally occurring antibodies (such as anti-A and anti-B) or immune antibodies that develop following a pregnancy or a transfusion.
Most often, HDFN is caused by the D antigen, although other Rh antigens, including c, C, E, and e, can be implicated as well.
HDFN has changed over the past few decades
With the use of anti–D immunoprophylaxis, HDFN linked to ABO incompatibility and other alloantibodies has become a major cause of this disorder in Western countries.
In fact, the administration of Rh immunoglobulin to RhD-negative mothers throughout their pregnancy and then shortly following the birth of a D-positive infant has dramatically decreased the incidence of Rh-hemolytic disease.
Read more about HDFN treatment
Diagnosis of HDFN today
Before giving birth, a mother can undergo certain tests to check for the presence of HDFN.
Blood tests can be obtained to see if the mother has antibodies against RBCs. A high-resolution ultrasound can be performed to study the fetus’s organs for any enlargement. If a fetus has anemia, the organs can be enlarged. Amniocentesis can also be performed. In this procedure, a small amount of amniotic fluid is collected and then examined in the laboratory to screen for the presence of any abnormalities.
Treatment of HDFN before the baby’s birth
Certain treatments and procedures may be utilized prior to the mother giving birth if a baby has been diagnosed with HDFN.
Laboratory tests can be conducted to determine the strength of the mother’s RBC antibodies. Ultrasound can be used to examine the flow of blood within the baby’s veins.
Occasionally, an intrauterine intravascular blood transfusion can be performed, in which the baby receives new RBCs to prevent the development of severe anemia. With this procedure, a needle is inserted into a vein in the umbilical cord and the blood is provided to the baby directly.
Sometimes, early delivery is suggested to prevent HDFN from worsening if the baby is becoming too large. Early delivery also may be recommended when severe complications are present and the infant’s lungs are considered sufficiently mature to sustain the birth process.
Laboratory monitoring of mother, fetus and newborn in HDFN
In their first trimester, all pregnant women undergo typing and screening. This helps to identify those who are RhD-negative at a gestational age (GA) of 25 weeks, who are subsequently offered a second screening test and a noninvasive prediction of fetal RhD.
At GA 29 weeks and again following delivery, RhD-negative women who are nonimmunized and are carrying an RhD-positive fetus are offered Rh immunoglobulin.
