Rh factor in obstetrics

Prepared by

Sattarova K.A.

Introduction Rh is the most important blood

group system after ABO in transfusion medicine.

One of the most complex of all RBC blood group systems with more than 50 different Rh antigens.

The genetics, nomenclature and antigenic interactions are unsettled.

This unit will concentrate on the most COMMONLY encountered observations, problems and solutions.

Antigens of Rh SystemTerms “D positive” and “D negative” refer only

to presence or absence of the Rh antigen D on the red blood cell.

Four additional antigens: C, c, E, e.MANY variations and combinations of the 5

principle genes and their products, antigens, have been recognized.The Rh antigens and

corresponding antibodies account for majority of unexpected antibodies encountered.

Rh antibodies stimulated as a result of transfusion or pregnancy, they are immune.

Clinical SignificanceD antigen, after A and B, is the most important RBC

antigen in transfusion practice. Individuals who lack D antigen DO NOT have anti-D. Antibody produced through exposure to D antigen through

transfusion or pregnancy. Immunogenicity of D greater than that of all other RBC

antigens studied.

Has been reported that 80%> of D neg individuals who receive single unit of D pos blood can be expected to develop immune anti-D.

Testing for D is routinely performed so D neg will be transfused with D neg.

Rh antibodies There are 3 types of Rh

antibodies: Agglutinating, Blocking, Hidden.

Agglutinating antibody give a visible agglutination with Rh positive red blood cells of null or homonymous group if they are suspended in serum, albumin, gelatin (incomplete antibodies) or in suspension of erythrocytes, in saline (complete antibody). Blocking antibodies is such antibodies that do not give a visible agglutination.

Hidden call these antibodies, which are only detected at a dilution with AB serum. Blocking antibodies not giving visible agglutination, there are block erythrocytes. With a lower molecular weight than the agglutinating antibodies, they are easily cross the placenta and are important in the pathogenesis of HDN.

Why Does Rh Status Matter?Fetal RBC cross to maternal circulation

Maternal immune system recognizes foreign antigens if fetus Rh + and mother Rh –

Antibodies are formed against fetal antigens

Subsequent pregnancy with Rh+ fetus, immune system activated

and large amounts of Ab formed

IgG Ab cross placenta & attack fetal RBC

Fetal anemia, hydrops, etc

Causes of RBC Transfer

abortion/ectopic blighted ovum antepartum bleeding special procedures (amniocentesis,

cordocentesis, CVS) external version platelet transfusion abdominal trauma inadvertent transfusion Rh+ blood postpartum (Rh+baby)

Hemolytic Disease of the Fetus

Hemolytic Disease of the Fetus (HDF)

A disorder of the fetus in which fetal red blood cells are destroyed by maternal IgG antibodies

The IgG antibodies cross the placenta and shorten red cell survival

The premature red cell destruction results in disease varying from mild anemia to death in uterus

Etiology in Fetus The mother is exposed during first pregnancy In a subsequent pregnancy, IgG antibodies cross the

placenta The antigens bind to fetal cells and red cells are

destroyed, liberating hemoglobin The hemoglobin is metabolized to indirect

hemoglobin Anemia occurs, which can lead to death

Blood group antigens and antibodies as applied to hemolytic disease of the fetus and newborn

Fetal death with maceration Early and rather

massive impact on the antibody unripe fetus, scarcity of morphological manifestations of the immaturity of the fetus.

Diagnosis is made by serology.

Edematous form Children are born pale, with

marked edema of the subcutaneous tissue, the presence of fluid in the cavities with enlarged liver and spleen. Jaundice is absent, since due to the high permeability of the placenta bilirubin passes into the mother's body and removes the bile. In the blood of the newborn a lot of young forms of red blood cells.

In most cases, death occurs.

Anemic form In hemolytic

disease of anemic form damaging effects on the fetus, usually small. At the forefront anemia, pale skin, hepatomegaly and splenomegaly.

Congenital icteric form occurs with significant

prenatal exposure to antibodies sufficiently ripe fetus. In this well-defined compensation adaptive mechanisms. Fetus is born with obvious signs of tension-type headache: anemia, enlargement of the liver, spleen. Developing or progressing jaundice, bilirubin encephalopathy.

Postnatal icteric form fetus is born

apparently healthy picture of the disease develops after a few hours or even 2-3 days after birth. Indirect bilirubin level is high and continues to grow. This causes serious intoxication, especially the brain.

The severity of the fetus

Mild form   Average

form Severe

anemia

Prediction of HDF Prenatal testing should be done D-negative mothers need to be identified Mothers who have antibodies capable of

causing HDF need to be identified Maternal history is also important

Antibody Titration Commonly used to predict severity of

HDFN Titer done early in pregnancy Repeated at 16 to 22 weeks and repeated

at 1- to 4-week intervalsA twofold rise in titer is an indication for further monitoringTo ensure significance, titers should be done using the same method and cells

Amniocentesis

Measurement of bilirubin in amniotic fluid can help indicate level of red cell destruction

Aspirated fluid is scanned on a spectrophotometer from 350 to 700 nm. The change in optical density above the baseline 450 nm is plotted on a Liley graph

Liley Graph

Interpretation of Liley Graph

Based on amniotic fluid analysis Three alternatives exist:

- Allow pregnancy to continue- Perform intrauterine transfusion- Induce labor

If labor is to be induced, L/S ratio needs to be done to determine fetal lung maturity

Postpartum Testing

Collect sample of cord blood Sample should be labeled and stored

up to 7 days All infants born to D-negative mothers

should be tested for D, including weak D

D-negative mothers of D-positive infants, including weak D-positive infants, are candidates for RhIG

Testing on Infants with Suspected HDFN

A diagnosis is based on medical history, physical examination, and lab testing on mother and infant

Tests to be performed:› ABO only forward type› D testing› Direct antiglobulin test if positive elution is

done › Eluate should be tested against A, B, and O

cells› Negative with all cells, low-frequency antibody

Determination of antibodies and their titer

Coombs' method, developed for use in forensic science and forensic medicine, later began to be used in obstetrics to detect Rh-antibodies. The method is based on the precipitation. Indirect test can detect red blood cells in cord blood of the newborn associated with antibodies (agglutination test of child's blood with a specific serum Coombs)

Nevertheless, the rise in antibody titer, particularly significant (3-4 orders of magnitude), take into account as an indirect sign of worsening of the HDFN.

distinguish: 1 Stable titre 2 Uniform titer increase 3 Uniform titer reduction 4 The sharp increase in titer before

delivery 5 The sharp drop in titer before delivery 6 Alternating ups and downs of antibodies

Course of Rh-sensitization Pregnancy

• Pregnant women often complain of general weakness, drowsiness, shortness of breath, a short loss of consciousness, frequent abdominal pain.

• In the first half of pregnancy toxicosis (50%), the threat of pregnancy termination (47%), hypotension (23%) manifest.

Course of Rh-sensitization Pregnancy

In the second half of pregnancy edema (13%), pre-eclampsia (16%), anemia observed.

Disturbances of mother’s live function

Chronic fetal hypoxia

Conducting of Rh-sensitization pregnancy

At patients with Rh(-) blood: Blood analysis for the presence of

antibodies and determining their titer: before 20 weeks of pregnancy it makes 1 time per month, after 20 weeks - ones every 2 weeks.

Indirect Coombs' test, which allows you to determine which antibodies circulate in the blood, associated or free.

Conducting of Rh-sensitization pregnancy

Ultrasound is performed every week starting from 31-32 weeks.

In pregnant women at high risk of FHD (a prior history of late miscarriage, premature birth, stillbirth) ultrasound should be performed daily or at an interval of 1-2 days.

Conducting of Rh-sensitization pregnancy

To reduce the sensitization of pregnant women with Rh-negative blood, even in the lack of Rh antibodies, as well as the presence of AB0-sensitization is recommended to 3 courses of nonspecific desensitizing therapy for 10-12 days during the term of 10-12, 22-24, 32-34 weeks.

Conducting of Rh-sensitization pregnancy

Pregnant women, has Rh sensitization should be sent to the maternity hospital at 34-36 weeks of gestation, at ABO sensitization it suppose to be 36-37 weeks for additional examination and decision on the delivery.

In the presence of the FHD need early delivery as in the end of pregnancy increases the flow of Rh antibodies to the fetus. The optimal timing of delivery - 37-38 weeks

In severe edematous form of FHD interrupt pregnancy at any stage.

Management of labor

Typically, delivery is performed vaginally. Caesarean section is performed in the presence of additional obstetric complications.

At readiness of the cervix produce amniotomy. If labors will not develop, within 5-6 hours after amniotomy begin labor induction with oxytocin or prostaglandins by the standard technique.

At birth through careful monitoring of the fetus, prevention of hypoxia.

Immediately after birth baby is quickly separated from the mother in order to avoid a massive hit Rh antibodies in the bloodstream of the newborn.

Umbilical cord blood is taken for determination of bilirubin, hemoglobin, blood group of the child, his Rh accessories.

Indirect Coombs test is carried out, allowing to detect red blood cells of the newborn associated with antibodies.

Given the propensity of the fetus and newborn with hemolytic disease to hemorrhage, must be handled carefully to the second stage of labor.

In the following, if it necessary carry out exchange transfusion for neonates with umbilical vessels, so brace on the umbilical cord do not impose.

Umbilical cord tied off at a distance of 2-3 cm from the umbilical ring.

Hyperbilirubinemia: Imbalance of bilirubin production and

elimination In order to clear from body must be:

› Conjugated in liver› Excreted in bile› Eliminated via urine and stool

Clinical Significance of Hyperbilirubinemia:

Most common reason that neonates need medical attention

“Physiologic jaundice” is a normal phenomenon during transition

Becomes concerning when levels continue to rise› Unconjugated

bilirubin is neurotoxic

Hyperbilirubinemia & Clinical Outcomes:

Deposits in skin and mucous membranes

Unconjugated bilirubin deposits in the brain

Permanent neuronal damage

JAUNDICE

ACUTE BILIRUBIN ENCEPHALOPATHY

KERNICTERUS

Clinical Symptoms: Acute Bilirubin

Encephalopathy/Kernicterus: › Irritability, jitteriness, increased high-pitched

crying› Lethargy and poor feeding› Back arching› Apnea› Seizures › Long-term: Choreoathetoid CP, upward gaze

palsy, SN hearing loss, dental dysplasia

Kernicterus:

* Bilirubin deposits typically in basal ganglia, hippocampus, substantia nigra, etc.

Diagnosis of HDN Degree family history obstetric

The clinical severity of the disease:

a) Group, Rh-blood baby accessory

b) Direct Coombs test (direct proportional relationship titer of jaundice)

c) Hb and erythrocytes in cord blood

d) Indirect bilirubin in the serum of umbilical cord blood ( in the dynamics to determine the hourly rates) (0.1 mg% per hour-an alarming sign)

Treatment of HDN.

The use of exchange transfusion for neonates with HDN, and the introduction of anti-Rhesus immunoglobulin mother (Rh IgG) after the termination of pregnancy) significantly reduced the high values of perinatal mortality and morbidity. Introduced Rh IgG, binds Rh-antigens that may enter the mother’s bloodstream during pregnancy termination, and thus prevent the production of material antibodies and Rh-immunization.

Treatment of HDN:

Drugs method: Vitamins. Hepatoprotectors, albumin

Exchange transfusion blood (180 ml of blood per 1 kg of the newborn)- Rh-negative

Indications for replace blood transfusions (RBT):

1) absolute indication for emergency RBT is hemolytic disease of the newborn;

2) indications for early RBT(within 24 hours) are:

- total bilirubin level in cord blood above 77.5 mmol/L; - hemoglobin level in cord blood less than 110 g/L (hematocrit less than 35%) - hourly increase of bilirubin higher than 8.5 mmol/L (rapidly progressive anemia), in this case it is recommended the substitution of blood in an amount equals to 2 blood volume;

Indications for replace blood transfusions (RBT):

3) only in the absence of the conditions necessary for the effective execution of a comprehensive conservative therapy can be used extended indications for early RBT:

- total bilirubin level in cord blood above 68 mmol/L - hemoglobin level in cord blood below 140g/L- jaundice in a child in the first 6h; - hourly increase of total bilirubin level above 6.8

mmol/l   In this case it’s also recommended the substitution of blood in an amount equals to 2 blood volume  

Indications for replace blood transfusions (RBT):

4) In the absence of indications for RBT in the first days of baby life the RBT should be made if the total serum bilirubin level is above 256 mmol /L on the second day of life, and more than 340 mmol /l in term and more than 256-340 mmol / l in preterm in the next days of life.

Selection of blood products and especially their use in the RBT:

1. for exchange transfusion with Rh-conflict they use Rh-negative blood of same group;

2. in case of group factors incompatibility it’s advisable to use packed red blood cells of 0 (I) group according to baby’s rhesus and plasma of the same group or AB (IV) group in a ratio of 2: 1;

3. in case of Rh factor incompatibility and blood group incongruity we should use the erythrocyte mass of 0 (I) a group Rh negative and plasma of AB (IV) groups in a ratio of 2: 1

Prevention of Rh-sensitization. any blood transfusions should be made

under the control of blood group and Rh compatibility between the recipient and the donor;

you need to save the first pregnancy in women with Rh-negative blood;

prevention and treatment of pregnancy complications;

holding desensitizing therapy; implementation of specific prevention of Rh

sensitization in women with Rh-negative blood by administering anti-Rhesus immunoglobulin after any termination of pregnancy.

Specific prevention of Rh- immunization is the injection of anti-D gamma globulin (preparation of Rogam) in the first 48-72 hours after birth (300 IU) or abortions (150 IU) to Rh-negative women. Specific condition: a woman should not be immunized during pregnancy. Antirhezus-immunoglobulin is administered one dose intramuscularly semelincidently. This dose is administered to puerperas within 48 hours after childbirth, in abortion – when the operation is completed. After cesarean section andmanual removal of the placenta the dose should be doubled.  

With strict implementation of techniques for specific prophylaxis of Rh sensitization the problem of Rh-conflict pregnancy can be almost solved!

Thank you for your attention