Rh – isoimmunization & ABO incompatibility

Prof. Zainab Babay

Rh – Iso-immunization

DefinitionPatho-physiologyPreventionManagement

Rh- Iso imunizationDefinition

known as:

,Rhesus incompatibility, Rhesus disease RhD Hemolytic Disease of the Newborn.

-When Rh –ve mother gets pregnant to Rh +ve fetus—she may be sensitized to Rh antigen and develop antibodies----these will cross the placenta and cause hemolysis of fetal red blood cells.

Rh- Iso imunization

When the disease is mild the fetus may have mild anemia with reticulocytosis .

-When the disease is moderate or severe the fetus can have a more marked anemia and erythroblastosis (erythroblastosis fetalis) .

-When the disease is very severe it can cause hydrops fetalis, or stillbirth.

Pathophysiology

-Usually due to Rhesus incompatibility.

-Other alloimmune antibody (Kell, Duffy, Kidd) can also cause hemolytic disease of the newborn.

Rh gene complex consists of 3 genetic loci each with 2 major alleles.

-They code for 5 major antigens denoted by letters, C, c, E, e, and D

-Rh antigen is not expressed on RBC progenitor.

-The exposure of the Rh-negative mother to Rh-positive red cells occurs as a result of asymptomatic feto-maternal hemorrhage during pregnancy.

Rh-Isoimmunization

Rh- Iso imunizationFetomaternal hemorrhage has been documented in:

7% in the first trimester. 16% in the second trimester

29% in the third trimester

Risk of fetromaternal hemorrhage is increased in abruption placenta, threatened abortion, toxemia, after cesarean section, ectopic pregnancy, amniocentesis, intrauterine fetal transfusion. And it occur during normal delivery

Rh- Iso imunization

After sensitization, maternal anti-D antibodies cross the placenta into fetal circulation---leading to hemolysis of fetal red blood cells & fetal anemia ( HB < 11 gm/dl).

If fetal hemoglobin is less than 4 gm/dl--- hydrops fetalis occur, fetal pleural effusion, fetal acsitis,generalized edema, & polyhydramnios.

Hyperbilirubinemia becomes apparent only in the delivered newborn because the placenta effectively metabolizes bilirubin.

Hyperbilirubinemia in the newborn lead to Kernictrus.

Rh- Iso imunizationIncidence

-1% of all pregnant women developed Rh alloimmunization.

-less than 10% requiring intrauterine transfusion.

-Anti-D is the most common antibodies found in pregnant women followed by anti-K, anti-c, and anti-E

-ABO incompatibility rarely lead to hemolysis (less than 1%)

Rh- Iso imunization

The first baby is normal

The second baby is anemic

The third baby on-ward will be hydrpoic

Rh- Iso imunization

Rh- Iso imunization

Body wall edema

hydropic fetus

Rh- Iso imunization

Fetal Ascites

Rh- Iso imunizationPrevention

-Screening of all pregnant mothers to Rh D antigen and antibody screening for Rh D –ve mothers.

-Prophylactic anti D immunoglobulin ( Rhogam) to all Rh –ve mothers after delivery if the fetus is Rh +ve or( at 28, 36 weeks of pregnancy) and after abortion, amniocentesis, abruption .

Rh- Iso imunizationPreventionThe standard dose of anti D is 0.3 mg —will eradicate 15 ml of fetal red blood cells (routine for all Rh –ve pregnancies) within 3 days of delivery.

-If more feto-maternal bleeding is suspected as in abruption or ante partum hemorrhage---Do Kleihauer –Betke test to estimate the amount of fetal red cells in maternal circulation and re-calculate the dose of the anti-D.

Management of the sensitized mother during pregnancy

-Initial Anti D titer at booking in early pregnancy & define the father antigen status.

-If antibody titer is +ve– repeat every 4 weeks.

-If titer rise or become 1:16 or higher—do serial amniocentesis from 16 -20 weeks on-ward for bilirubin level and blot liley curve which predict severity of the disease.

Management of the sensitized mother during pregnancy

-Zone 1 suggest mildly affected fetus and repeat amniocentesis in 2-3 weeks.

-Zone 2 suggest moderately affected fetus and repeat amniocentesis in 1-2 weeks.

-Zone 3 suggest severely affected fetus ---do Umbilical blood sampling (PUBS) to obtain fetal Hb & hematocrit & perform intra-uterine transfusion.

Current guidelines for management of Rh sensitized mothers

-Serial ultrasound fetal assessment for early signs of fetal anemia and hydrops (Peak systolic middle cerebral artery Doppler velocimetry MCA) starting at 18 weeks and repeated every 3-4 weeks.

MCA Doppler

Current guidelines for management of Rh sensitized mothers

-If fetal Hb is dropped less than 11gm/dl or HCT less than 30%--- intrauterine fetal blood transfusion is indicated –repeated every 3-4 weeks until delivery at 34 weeks.

Steroid for fetal lung maturation before procedure

Differential diagnosis of hydropic fetusAnemia, AcuteParvovirus B19 InfectionAtrial FlutterSyphilis

Cardiac Tumors or cardiac abnormalityToxoplasmosisCytomegalovirus InfectionTyrosinemiaGalactose-1-Phosphate Uridyltransferase Deficiency (Galactosemia)Hydrops FetalisHypothyroidismhemogloninopathy

Management of sensitized newborn

-Mild anemia (Hb <14gm/dl, cord bilirubin>4 mg/dl)---Phototherapy

-Moderate to severe----Exchange transfusion.

-Mild Hydrops improves in 88% of cases

-Severe hydrops—Mortality is 39%

Thank you