Hemolytic disease of the newborn (ABO)
Encyclopedia
In ABO hemolytic disease of the newborn (also known as ABO HDN) maternal IgG antibodies with specificity for the ABO blood group system
pass through the placenta
to the fetal circulation where they can cause hemolysis
of fetal red blood cells which can lead to fetal anemia
and HDN
. In contrast to Rh disease
, about half of the cases of ABO HDN occur in a firstborn baby and ABO HDN does not become more severe after further pregnancies.
The ABO blood group system is the best known surface antigen system, expressed on a wide variety of human cells. For Caucasian
populations about one fifth of all pregnancies have ABO incompatibility between the fetus and the mother, but only a tiny minority develop symptomatic ABO HDN. The latter only occurs in mothers of blood group O because they can produce enough IgG antibodies to cause hemolysis.
Although very uncommon, cases of ABO HDN have been reported in infants born to mothers with blood groups A and B.
Anti-A and anti-B antibodies are usually IgM
and do not pass through the placenta, but some mothers "naturally" have IgG anti-A or IgG anti-B antibodies, which can pass through the placenta. Exposure to A-antigens and B-antigens, which are both widespread in nature, usually leads to the production of IgM anti-A and IgM anti-B antibodies but occasionally IgG antibodies are produced.
Some mothers may be sensitized by fetal-maternal transfusion of ABO incompatible red blood and produce immune IgG antibodies against the antigen they do not have and their baby does. For example, when a mother of genotype OO (blood group O
) carries a fetus of genotype AO (blood group A) she may produce IgG anti-A antibodies. The father will either have blood group A, with genotype AA or AO, or more rarely, have blood group AB, with genotype AB.
It would be very very rare for ABO sensitization to be caused by therapeutic blood transfusion
as a great deal of effort and checking is done to ensure that blood is ABO compatible between the recipient and the donor.
antibody screening blood tests (indirect Coombs test) do not screen for ABO HDN. If IgG anti-A or IgG anti-B antibodies are found in the pregnant woman's blood, they are not reported with the test results, because they do not correlate well with ABO HDN. Diagnosis is usually made by investigation of a newborn baby who has developed jaundice
during the first day of life.
caused by ABO HDN is usually successfully treated with phototherapy, unless the ABO HDN is uncommonly severe. Treatment of moderate or severe HDN caused by ABO antibodies is similar to that for Rh disease
.
ABO blood group system
The ABO blood group system is the most important blood type system in human blood transfusion. The associated anti-A antibodies and anti-B antibodies are usually IgM antibodies, which are usually produced in the first years of life by sensitization to environmental substances such as food,...
pass through the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
to the fetal circulation where they can cause hemolysis
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
of fetal red blood cells which can lead to fetal anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
and HDN
Hemolytic disease of the newborn
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an alloimmune condition that develops in a fetus, when the IgG molecules produced by the mother pass through the placenta...
. In contrast to Rh disease
Rh disease
Rh disease is one of the causes of hemolytic disease of the newborn...
, about half of the cases of ABO HDN occur in a firstborn baby and ABO HDN does not become more severe after further pregnancies.
The ABO blood group system is the best known surface antigen system, expressed on a wide variety of human cells. For Caucasian
Caucasian race
The term Caucasian race has been used to denote the general physical type of some or all of the populations of Europe, North Africa, the Horn of Africa, Western Asia , Central Asia and South Asia...
populations about one fifth of all pregnancies have ABO incompatibility between the fetus and the mother, but only a tiny minority develop symptomatic ABO HDN. The latter only occurs in mothers of blood group O because they can produce enough IgG antibodies to cause hemolysis.
Although very uncommon, cases of ABO HDN have been reported in infants born to mothers with blood groups A and B.
Causes
- Environmental exposure
Anti-A and anti-B antibodies are usually IgM
IGM
IGM as an acronym or abbreviation can refer to:* Immunoglobulin M , the primary antibody against A and B antigens on red blood cells* International Grandmaster, a chess ranking* intergalactic medium* Intragroup medium - see: Intracluster medium...
and do not pass through the placenta, but some mothers "naturally" have IgG anti-A or IgG anti-B antibodies, which can pass through the placenta. Exposure to A-antigens and B-antigens, which are both widespread in nature, usually leads to the production of IgM anti-A and IgM anti-B antibodies but occasionally IgG antibodies are produced.
- Fetal-maternal transfusion
Some mothers may be sensitized by fetal-maternal transfusion of ABO incompatible red blood and produce immune IgG antibodies against the antigen they do not have and their baby does. For example, when a mother of genotype OO (blood group O
ABO blood group system
The ABO blood group system is the most important blood type system in human blood transfusion. The associated anti-A antibodies and anti-B antibodies are usually IgM antibodies, which are usually produced in the first years of life by sensitization to environmental substances such as food,...
) carries a fetus of genotype AO (blood group A) she may produce IgG anti-A antibodies. The father will either have blood group A, with genotype AA or AO, or more rarely, have blood group AB, with genotype AB.
- Blood transfusion
It would be very very rare for ABO sensitization to be caused by therapeutic blood transfusion
Blood transfusion
Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...
as a great deal of effort and checking is done to ensure that blood is ABO compatible between the recipient and the donor.
Moderating factors
In about a third of all ABO incompatible pregnancies maternal IgG anti-A or IgG anti-B antibodies pass through the placenta to the fetal circulation leading to a weakly positive direct Coombs test for the neonate's blood. However, ABO HDN is generally mild and short-lived and only occasionally severe because:- IgG anti-A (or IgG anti-B) antibodies that enter the fetal circulation from the mother find A (or B) antigens on many different fetal cell types, leaving fewer antibodies available for binding onto fetal red blood cells.
- Fetal RBCRed blood cellRed blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
surface A and B antigens are not fully developed during gestation and so there are a smaller number of antigenic sites on fetal RBCs.
Diagnosis
Routine antenatalObstetrics
Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...
antibody screening blood tests (indirect Coombs test) do not screen for ABO HDN. If IgG anti-A or IgG anti-B antibodies are found in the pregnant woman's blood, they are not reported with the test results, because they do not correlate well with ABO HDN. Diagnosis is usually made by investigation of a newborn baby who has developed jaundice
Jaundice
Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
during the first day of life.
Treatment
Neonatal jaundiceNeonatal jaundice
Neonatal jaundice or Neonatal hyperbilirubinemia is a yellowing of the skin and other tissues of a newborn infant. A bilirubin level of more than 85 umol/l manifests clinical jaundice in neonates whereas in adults a level of 34 umol/l would look icteric...
caused by ABO HDN is usually successfully treated with phototherapy, unless the ABO HDN is uncommonly severe. Treatment of moderate or severe HDN caused by ABO antibodies is similar to that for Rh disease
Rh disease
Rh disease is one of the causes of hemolytic disease of the newborn...
.
See also
- Coombs testCoombs testCoombs test refers to two clinical blood tests used in immunohematology and immunology...
- Hemolytic anemiaHemolytic anemiaHemolytic anemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells , either in the blood vessels or elsewhere in the human body . It has numerous possible causes, ranging from relatively harmless to life-threatening...
- HematologyHematologyHematology, also spelled haematology , is the branch of biology physiology, internal medicine, pathology, clinical laboratory work, and pediatrics that is concerned with the study of blood, the blood-forming organs, and blood diseases...