Hameolytic Disease Of Foetus/newborn Flashcards
What is Hefner?
Life span of foetus/newborn red blood cell is shortened due to passively aquired antibody of mothers origin
Ig antibody produce by mother cross placenta, bind to fetal RBC and casue hemoolysis
Anti-RhD most common
Translacental leaks cause small volume of RBC to pass to maternal circulation during pregnancy
Mother is exposed to fetalRBC which some is foreign as its paced from the fatherr
What happens when the foreign anti gents exposed to mother
Fetal circulation = fetal RBC express antigens that maternal RBC do not
Mothers immune system stimulates and produced antibodies to foreign antigens
Placenta is the barrier but some could still leak
During te 2nd pregnancy, specific IgG molecules targeted towards the fetal RBC antigen across placenta and attach to fetal RBC
Histamine binding causes sensitisation of RBC and destruction destruction yh reticuloendothelial system
IgG cited RBC cant pass through spleen causing hemalysis, complemen system activated contributing to hemolysis
Cases with RhD- mother and RhD+ baby
RhD+father passes down D antigen to baby
Child is heterozzygous for RHD gene Anne have RHD+
Sometimes RHD- others and RhD+ dont stimulate maternal production o anti-RhD because the volume of RBC is too low to beimmunoenic, other has 16%chanceof making anti-RhD
Second pregnancy
IgG crosses placneta during first trimester
Betweeen 16-20 weeks anti-D can go across places and casue death , Riss as gestation continues.
Maternal antibody production
Macrophage recognise and engulf RBC
RhD antigen are presented on macrophages surface on MHC class 11 molecules
Macrophage produces cytokines that attract b-cells and t cells to area and form complex
B-cels are activated and turn into plasma cells and replicate, producing large amounts of antibodies, some differentiate into memory b - cells which remain in circulation for years showing cell surface receptor specific for RhD antigen
What effect does this have on foetus
Fetal anemia
Extravascula heolysis
Heptospenomegaly
Subcutaneous EDEMA
Buildup of bilirubin in brain tissue-brain damage ( kernicterus)
Effect it s on infant
Asphyxia
Pulmonary hypertension
Pallor
EDEMA
Respiratory distress
Coagulopathies
Jaundice
Kernicterus
Hypocalamia
Tests
Kleihauer-Betke 9KB) test-
Flow cytometry, identifies fetal RBC in maternal blood sample
DAT- detec IgG antibodies bound to fetal RBC
IAT detect antibodies in maternal plasma that can bind tp fetalRBC ntigens
Antenatal ultrasound scan; detect sign of hydrosphereftlis
Kleihauer-Betke
Test for quantifying foetal-maternal haemorrhage
Treats maternal blood sample with an acid which ashes out Hb leaving he more antireistant foetal hb
Nader microscope u can we the ratio of material-foetal haemorrhage making sure we give the correct dose of anti- D immunoglobulin
U can also test using direct anti globulin which detects IgG antibodies in foetal RBC or IAT to check material antibodies in mothers plasma that may be reactive against fiesta RBC
