Rh disease

Rh disease (also known as rhesus isoimmunisation, Rh (D) disease, rhesus incompatibility, rhesus disease, RhD hemolytic disease of the newborn, rhesus D hemolytic disease of the newborn or RhD HDN) is a type of hemolytic disease of the newborn (HDN). The disease ranges from mild to severe, and typically occurs only in some second or subsequent pregnancies of Rh negative women where the fetus's father is Rh positive, leading to a Rh+ pregnancy. During birth, the mother may be exposed to the infant's blood, and this causes the development of antibodies, which may affect the health of subsequent Rh+ pregnancies. In mild cases, the fetus may have mild anaemia with reticulocytosis. In moderate or severe cases the fetus may have a more marked anaemia and erythroblastosis fetalis (hemolytic disease of the newborn). When the disease is very severe it may cause hydrops fetalis or stillbirth.

Rh disease is generally preventable by treating the mother during pregnancy or soon after delivery with an intramuscular injection of anti-RhD immunoglobulin (Rho(D) immune globulin). The RhD protein is coded by the RHD gene.

Serology

During any pregnancy a small amount of the baby's blood can enter the mother's circulation. If the mother is Rh negative and the baby is Rh positive, the mother produces antibodies (including IgG) against the rhesus D antigen on her baby's red blood cells. During this and subsequent pregnancies the IgG is able to pass through the placenta into the fetus and if the level of it is sufficient, it will cause destruction of rhesus D positive fetal red blood cells leading to the development of Rh disease. It may thus be regarded as insufficient immune tolerance in pregnancy. Generally rhesus disease becomes worse with each additional rhesus incompatible pregnancy.

The main and most frequent sensitizing event is child birth (about 86% of sensitized cases), but fetal blood may pass into the maternal circulation earlier during the pregnancy (about 14% of sensitized cases).^[1] Sensitizing events during pregnancy include c-section, miscarriage, therapeutic abortion, amniocentesis, ectopic pregnancy, abdominal trauma and external cephalic version. However, in many cases there was no apparent sensitizing event.

The incidence of Rh disease in a population depends on the proportion that are rhesus negative. Many non-Caucasian people have a very low proportion who are rhesus negative, so the incidence of Rh disease is very low in these populations. In Caucasian populations about 1 in 10 of all pregnancies are of a rhesus negative woman with a rhesus positive baby. It is very rare for the first rhesus positive baby of a rhesus negative woman to be affected by Rh disease. The first pregnancy with a rhesus positive baby is significant for a rhesus negative woman because she can be sensitized to the Rh positive antigen. In Caucasian populations about 13% of rhesus negative mothers are sensitized by their first pregnancy with a rhesus positive baby. Without modern prevention and treatment, about 5% of the second rhesus positive infants of rhesus negative women would result in stillbirths or extremely sick babies. Many babies who managed to survive would be severely ill. Even higher disease rates would occur in the third and subsequent rhesus positive infants of rhesus negative women. By using anti-RhD immunoglobulin (Rho(D) immune globulin) the incidence is massively reduced.

Rh disease sensitization is about 10 times more likely to occur if the fetus is ABO compatible with the mother than if the mother and fetus are ABO incompatible.

Prevention

Most Rh disease can be prevented by treating the mother during pregnancy or promptly (within 72 hours) after childbirth. The mother has an intramuscular injection of anti-Rh antibodies (Rho(D) immune globulin). This is done so that the fetal rhesus D positive erythrocytes are destroyed before the immune system of the mother can discover them and become sensitized. This is passive immunity and the effect of the immunity will wear off after about 4 to 6 weeks (or longer depending on injected dose) as the anti-Rh antibodies gradually decline to zero in the maternal blood.

It is part of modern antenatal care to give all rhesus D negative pregnant women an anti-RhD IgG immunoglobulin injection at about 28 weeks gestation (with or without a booster at 34 weeks gestation). This reduces the effect of the vast majority of sensitizing events which mostly occur after 28 weeks gestation. Giving Anti-D to all Rhesus negative pregnant women can mean giving it to mothers who do not need it (because her baby is Rhesus negative or their blood did not mix).^[2] Many countries routinely give Anti-D to Rhesus D negative women in pregnancy. In other countries, stocks of Anti-D can run short or even run out.^[2] Before Anti-D is made routine in these countries, stocks should be readily available so that it is available for women who need Anti-D in an emergency situation.^[2]

A recent review found research into giving Anti-D to all Rhesus D negative pregnant women is of low quality.^[2] However the research did suggest that the risk of the mother producing antibodies to attack Rhesus D positive fetal cells was lower in mothers who had the Anti-D in pregnancy.^[2] There were also fewer mothers with a positive kleihauer test (which shows if the mother’s and unborn baby’s blood has mixed).^[2] Anti-RhD immunoglobulin is also given to non-sensitized rhesus negative women immediately (within 72 hours—the sooner the better) after potentially sensitizing events that occur earlier in pregnancy.

The discovery of cell-free DNA in the maternal plasma has allowed for the non-invasive determination of the fetal RHD genotype. In May 2017, the Society for Obstetrics and Gynecology of Canada is now recommending that the optimal management of the D-negative pregnant woman is based on the prediction of the fetal D-blood group by cell-free DNA in maternal plasma with targeted antenatal anti-D prophylaxis.^[3] This provides the optimal care for D-negative pregnant women and has been adopted as the standard approach in a growing number of countries around the world. It is no longer considered appropriate to treat all D-negative pregnant women with human plasma derivatives when there are no benefits to her or to the fetus in a substantial percentage of cases.

Blood tests

Maternal blood

• The Kleihauer–Betke test or flow cytometry on a postnatal maternal blood sample can confirm that fetal blood has passed into the maternal circulation and can also be used to estimate the amount of fetal blood that has passed into the maternal circulation.
• The indirect Coombs test is used to screen blood from antenatal women for IgG antibodies that may pass through the placenta and cause hemolytic disease of the newborn.
• Free Cell DNA can be run on certain antigens. Blood is taken from the mother, and using PCR, can detect the K, C, c, D, and E alleles of fetal DNA. This blood test is non-invasive to the fetus and is an easy way of checking antigen status and risk of HDN. Testing has proven very accurate and is routinely done in the UK at the International Blood Group Reference Laboratory in Bristol.^[4] Sanequin laboratory in Amsterdam, Netherlands also performs this test. For US patients, blood may be sent to either of the labs. In the US, Sensigene is done by Sequenome to determine fetal D status. Sequenome does not accept insurance in the US, but US and Canadian patients have had insurance cover the testing done overseas.

Paternal Blood

Blood is generally drawn from the father to help determine fetal antigen status.^[5] If he is homozygous for the antigen, there is a 100% chance of all offspring in the pairing to be positive for the antigen and at risk for HDN. If he is heterozygous, there is a 50% chance of offspring to be positive for the antigen.^[6] This test can help with knowledge for the current baby, as well as aid in the decision about future pregnancies. With RhD, the test is called the RhD genotype. With RhCE, and Kell antigen it is called an antigen phenotype.^[7]

Fetal blood (or umbilical cord blood)

• The direct Coombs test is used to confirm that the fetus or neonate has an immune mediated hemolytic anemia.
• Full blood count—the hemoglobin level and platelet count are important
• Bilirubin (total and indirect)

In some cases, the direct coombs will be negative but severe, even fatal HDN can occur.^[8] An indirect coombs needs to be run in cases of anti-C,^[9] anti-c,^[9] and anti-M. Anti-M also recommends antigen testing to rule out the presence of HDN.^[10]

• Hgb - the infant’s hemoglobin should be tested from cord blood.^[11]
• Reticulocyte count - Reticulocytes are elevated when the infant is producing more blood to combat anemia.^[11] A rise in the retic count can mean that an infant may not need additional transfusions.^[12] Low retic is observed in infants treated with IUT and in those with HDN from anti-Kell^[9]
• Neutrophils - as Neutropenia is one of the complications of HDN, the neutrophil count should be checked.^[13][14]
• Thrombocytes - as thrombocytopenia is one of the complications of HDN, the thrombocyte count should be checked.^[13]
• Bilirubin should be tested from cord blood.^[11]
• Ferritin - because most infants affected by HDN have iron overload, a ferritin must be run before giving the infant any additional iron.^[15]
• Newborn Screening Tests - Transfusion with donor blood during pregnancy or shortly after birth can affect the results of the Newborn Screening Tests. It is recommended to wait and retest 10–12 months after last transfusion. In some cases, DNA testing from saliva can be used to rule out certain conditions.

Management

Antenatal

• Serial Ultrasound and Doppler examinations—to detect signs of fetal anemia such as increased blood flow velocities and monitor hydrops fetalis
• Quantitative analysis of maternal anti-RhD antibodies—an increasing level is a sign of fetal Rh disease
• Intrauterine blood transfusion
  • Intraperitoneal transfusion—blood transfused into fetal abdomen
  • Intravascular transfusion—blood transfused into fetal umbilical vein—This is the method of choice since the late 1980s, and more effective than intraperitoneal transfusion. A sample of fetal blood can be taken from the umbilical vein prior to the transfusion.
• Early delivery (usually after about 36 weeks gestation)

Postnatal

• Phototherapy for neonatal jaundice in mild disease
• Exchange transfusion if the neonate has moderate or severe disease (the blood for transfusion must be less than a week old, Rh negative, ABO compatible with both the fetus and the mother, and be cross matched against the mothers serum)
• IVIG has been used to successfully treat many cases of HDN. It has been used not only on anti-D, but on anti-E as well.^[16] IVIG can be used to reduce the need for exchange transfusion and to shorten the length of phototherapy.^[17] The AAP recommends "In isoimmune hemolytic disease, administration of intravenousγ-globulin (0.5-1 g/kg over 2 hours) is recommended if the TSB is rising despite intensive phototherapy or the TSB level is within 2 to 3 mg/dL (34-51 μmol/L) of the exchange level . If necessary, this dose can be repeated in 12 hours (evidence quality B: benefits exceed harms). Intravenous γ-globulin has been shown to reduce the need for exchange transfusions in Rh and ABO hemolytic disease."^[18]

History of medical advances in Rh disease

The rhesus blood type was first discovered in 1937 by Karl Landsteiner and Alexander S. Wiener,^[19] who listed it in and alongside their tables for blood-typing and cross-matching.

In 1939 Philip Levine and Rufus E. Stetson published their findings about a family who had a stillborn baby who died of hemolytic disease of the newborn.^[20] The mother was aged 25 and it was her second pregnancy and she suffered blood loss at the delivery. Both parents were blood group O and the husband's blood was used to give the mother a blood transfusion, but the mother suffered a severe transfusion reaction. They investigated this transfusion reaction. Since the mother and the father were both blood group O, they concluded that there must be a previously undiscovered blood group antigen that was present on the husband's RBCs (red blood cells) but was not present on the mother's RBCs and that the mother had formed antibodies against the new blood group antigen. This suggested for the first time that a mother could make blood group antibodies because of immune sensitization to her fetus's RBCs. They did not name this blood group antigen, but it was subsequently found to be the rhesus factor.

The first treatment for Rh disease was an exchange transfusion, which was invented by Alexander S. Wiener. That procedure was further refined by Harry Wallerstein,^[21] a transfusionist. Although the most effective method of treating the problem at the time, it was only partially ameliorative in cases where damage to the neonate had already been done. Children with severe motor damage and/or retardation could result. However, it is estimated that in the two decades it was used approximately 200,000 lives were saved, and the great majority were not brain damaged.

Ronald Finn, in Liverpool, England applied a microscopic technique for detecting fetal cells in the mother's blood. It led him to propose that the disease might be prevented by injecting the at-risk mother with an antibody against fetal red blood cells. He proposed this for the first time to the public on February 18, 1960. A few months later, he proposed at a meeting of the British Genetical Society that the antibody be anti-RhD.

Nearly simultaneously with him, William Pollack, then of Ortho Pharmaceutical Corporation, and researchers John Gorman and Vincent Freda of New York City's Columbia-Presbyterian Medical Center,^[22] having come to the same realization, set out to prove it by injecting a group of male prisoners at Sing Sing Correctional Facility with antibody provided by Ortho, obtained by a fractionation technique developed by Pollack (who also provided Finn with several vials of antibody during a visit by Finn to Ortho).

Animal studies had previously been conducted by William Pollack, using a rabbit model of Rh. This model, named the rabbit HgA-F system, was a perfect animal model of human Rh, and enabled Pollack's team to gain experience in preventing hemolytic disease in rabbits by giving specific HgA antibody, as was later done with Rh-negative mothers. One of the needs was a dosing experiment that could be used to determine the level of circulating Rh-positive cells in an Rh-negative pregnant female derived from her Rh-positive fetus. This was first done in the rabbit system, but subsequent human tests at the University of Manitoba conducted under Pollack's direction confirmed that this result matched the human dosing perfectly. The dose is 20 µG of antibody for 1mL of Rh-positive red cells.

Sir William Liley performed the first successful intrauterine transfusion in 1963.

Gorman's sister-in-law was the first at risk woman to receive a prophylactic injection on January 31, 1964. Clinical trials set up by Pollack in 42 clinical centers in the US, Great Britain, Germany, Sweden, Italy, and Australia confirmed their hypothesis, and the vaccine was finally approved in England and the United States in 1968. The FDA approved the drug under the name RhoGAM, with a fixed dose of 300 µG, to be given within three days postpartum. There being no known harm done by delaying the dosage for a week or more after birth, Ortho asked the FDA to grant permission for it to be given without a postpartum time restriction. In addition, John M. Bowman, one of the researchers at the University of Manitoba, and Freda pushed to allow antepartum use. All of this was subsequently granted. Within a year or so, the antibody had been injected with great success into more than 500,000 women. Time magazine picked it as one of the top ten medical achievements of the 1960s. By 1973, it was estimated that in the US alone, over 50,000 babies' lives had been saved. The use of Rh immune globulin to prevent the disease in babies of Rh negative mothers has become standard practice, and the disease, which used to claim the lives of 10,000 babies each year in the US alone, has been virtually eradicated in the developed world. The achievement was made almost entirely without support from the NIH, who rejected the New York group's proposal twice. The group got instead only a small grant ($329,765 over 10 years) from the City of New York. The total cost of the effort was only a couple of million dollars, which is about the cost of the life-time care of a half-dozen irreparably brain-damaged children. In 1980, Cyril Clarke, Ronald Finn, John Gorman, Vincent Freda, and William Pollack each received an Albert Lasker Award for Clinical Medical Research for their work on rhesus blood types and the prevention of Rh disease.

Two of the Canadian researchers from the University of Manitoba, Bruce Chown, John M. Bowman and under the leadership of the President of the Winnipeg Rh Institute, Albert D. Friesen, PhD, licensed a version of the vaccine, known as WinRho, in 1980. The drug is sold in 35 countries by the Manitoba-based research firm Cangene, listed on the Toronto Stock Exchange with worth of about $175 million. Cangene was purchased by the Winnipeg Rh Institute, a facility founded by Chown and Bowman and dedicated to conducting research into blood related diseases. Chown is honored by the Canadian Medical Hall of Fame for his lifelong work with erythroblastosis fetalis.

James Harrison, OAM, also known as the Man with the golden arm, is a blood plasma donor from Australia. He has made over 1000 donations throughout his lifetime, and these donations are estimated to have saved over two million unborn babies from the condition. Up to 2015, every batch of anti-D in Australia was made from his blood.^[23]

Transfusion Reaction

Once a woman has antibodies, she is at high risk for a transfusion reaction.^[24] For this reason, she must carry a medical alert card at all times and inform all doctors of her antibody status.

See also

• Hemolytic disease of the newborn
• Coombs test
• Hemolytic anemia
• Hematology
• Sperm donation
• James Harrison

References

• Friesen A.D., Bowman J.M., Price H.W. (1981). "Column Ion Exchange Preparation and Characterization of an Rh Immune Globulin (WinRho) for Intravenous Use". J. Appl. Biochem. 3: 164–175. CS1 maint: Multiple names: authors list (link)

External links

• National institute of Clinical Excellence (NICE) Guidelines for anti-D prophylaxis
• "Rh Incompatibility in Pregnancy" by N. Antonios at the Embryo Project Encyclopedia
• A review of the clinical effectiveness and cost-effectiveness of routine anti-D prophylaxis for pregnant women who are rhesus-negative, from the National Health Service Technology Assessment Programme.
• Intrauterine fetal blood transfusion for Rh disease
• Summary of transfusion reactions in the US