presence of RH antibodies in RH –ve maternal circulationincidence : 45\ 1000 deliveries 10\1000 deliveries Pathophysiology RH : presence of D antigen 15% of white 8% black 2% asian
transfusion of improperly cross matched blood feto-matermal transplacental haemorrhage(TPH) silent abortion ectopic chorionic villus sampling amniocentesis APH external cephalic version postpartum haemorrhage
when rh positive cells enter maternal circulation primary immune respose is by IGM antibodies , secondery immune response is by IGG antibodies which capable of crossing the placenta IMMUNIZATION depend on : amount of blood transfused > 0.25 ml ABO status of the fetus ABO compatible : 16% ABO incompatible : 1-2 %
when maternal antibodies cross placenta ,attack RH antigen on fetal RBC ,non – complement mediated hemolysis occurred resulte in fetal anaemia which in turn stimulate extramedullary erythropoeisis in fetal liver ( hypoproteinaemia , portal hypertension) - fetal anaemia causes hypoxia , capillary leakage, combination result in hydrops
administration of RH immunoglobulin mechanism of action timing of administration 72hrs Dose 500iu =100mg before do estimate of fetal blood in maternal circulation by Kleihaur test under 50 lpf each 5 RBC equivelent = o.25ml 500iu = 4ml = 80cell in lpf o+VE gastric acid resistant capsule bone marrow transplant plasmaphoresis.
during delivery : hurry removal of placenta avoid unnecessary spillage of blood in peritoneal cavity amniocentesis done under USS Treatment RH negative non immunized at least 2 blood samples for blood group & RH antibodies titre screening at booking , 18wks ,32 wks anti D to mother with V.B of unknown origin at delivery : indirect coombs test to the mother, kleihaur test , give anti D
Mildly affected : when titre level less than 1 : 16 or 4iu do monthly antibodies titre no invasive fetal evalution follow up by USS delivery at term moderately or severly affected depened on past obstetric history and antibodies titre fetal genotyping USS amount of amniotic fluid fetal spleen and liver size
placental thickness bowel echogenicity cardiac size Doppler USS : screening for fetal anemia by assessing blood flow velocity especialy in cerebral artery fetal hematocrite two invasive method : direct indirect direct by Cordocentesis to assess blood grouping &Rh direct coombs test, PCV , reticulocyte count, bilirubin level indirect : by spectrophotometry
by using sample of amniotic fluid obtaind by amniocentesisand assess level of bilirubin which reflect relatively fetal hematocrit this level can be plotted against gestational age in what we call it LILEY s chart which divided into three zones Zone 1 : mildly affected …. repeat after 4 weeks , delivery at term ….rarely affected neonateZone 2 : moderatly affected ….. repeat after one week , delivery depend on gestational age Zone3 : severly affected fetus ….. need urgent interference by either :Intrauterine transfusionDelivery
IUTtwo types of intrauterine transfusion :intraperitoneal intravasculardone only when fetus is hydropic or severly aneamic pcv = or <30% use fresh o –ve blood irradiated RBC pcv = 90%under continouse fetal heart monitoring