Dr. Enass Saleh Al-Khayat
ObstetricsRheusus iso-Immunization
L 2
2. Management of sensitized Rh-ve pregnant :
The aim of the management is to : detect the fetal affection earlier and detect its severity ( mild , moderate , severe anemia ) , it deal with it either by intrauterine therapy , or postnatally and timing the delivery to reduce fetal mortality and morbidity .
* We repeat the antibody(Ab) titer every 2 4 wks , and if Ab titer is not increasing , this indicate no further sensitization , but when the titer reach to critical value ≥ 1/16 , then this indicate to the need of immediate intervention and it is better to measure the level of Abs by international units / ml without titration because titration does not always correlates with severity of fetal hemolytic disease , a woman with anti D < 4 IU / ml , we check maternal serum Ab/ 4wks , if remain less than 4 IU / ml , then the fetus is unlikely to be affected and induction of labour at 38 40 wks is only intervention required in antenatal period . The rapid increasing the titer or Ab level > 4 IU / ml indicate serious condition and need intervention , according to degree of affection ( amniocentesis + cordocentesis with U/S evaluation) if :
1. Mildly affected fetus : we do the following : maternal plasmaphoresis , early preterm delivery (≥ 34 wks ) + intensive neonatal care ( photo therapy ,etc
2. Moderate to sever affection managed in a specialized center need follow up closely :
A- If gestational age > 34 wks : ( mature lung ) by ( L/S ratio ) delivery and neonatal care ( investigation , exchange transfusion , especially if the Hb% is low ( < = 5g/dl ) .
B- If GA < 34 wks gestation : especially if there is a history of previous severely affected pregnancy ( hydrops or IUD , stillbirth etc ) intrauterine management and close follow up by :
1. a non invasive methods :
A- high resolution U/S : Sonographic finding predicting sever anemia and preceeding hydrops fetalis :
1. Increase amniotic fluid index .
2. Increase liver and spleen ( length and thickness )
3. Increase placental thickness ( oedematous )
4. Increase bowel echogenicity .
5. Increase cardiac biventricular diameter .
B- Doppler study of fetal middle cerebral artery , increased peak velocity related to fetal anemia ( up to 35 wks ) .The sensitivity is reported at 100%with a false positive rate of 12%.
C- Serial electronic fetal heart monitoring , demonstrating a specific pattern ( sinusoidal rhythm ) and non stress test non reactive result .
2- Invasive methods :
1. Amniotic fluid spectrophotometry .
There is an excellent correlation between the amount of biliary pigment in amniotic fluid and fetal hematocrit , beginning at 27 wks of gestation , may be earlier ( in severity affected fetus or with previous affected baby (beginning at 10 wks before its occurrence) .
* We aspirate ( 10 cc ) of fluid under U/S guide and transferred in dark tube and unconjecated bilirubin level measured at Delta-optical density 450 (nm ) wave length by spectrophotometric analysis .
- The result is potted on a spectrophotometric graph called ( Liley graph ) , using this method to establish predictive zones for mild , moderate and severe diseases the liley chart can be used to determine with accuracy the severity of the disease and the appropriate management beginning at 27 wks gestation .
* The Queenan chart ( curve ) : a modified Liley curve with 4 zones instead of 3 . Is used a procedure tool in some centers from 14 40 wks gestation .
* The incidence of FMH is reported to be 8.4 11% per procedure . Serial amniocentesis is generally indicated ( because single Delta optical density 450 values are helpful only if they are very high ( zone III ) or very low ( zone I ) , falling of Delta O.D. 450 values are indicative of fetus that is either unaffected ( Rh-ve fetus ) or very mildly affected no intervention indicated .
if the Delta O.D. 450 is either stable or rising frequent Delta O.D. 450 determinations are necessary , if Delta O.D. 450 enter zone II or III after 34 wks of gestations , determine lung maturity delivery .
If enter zone II or III before 34 wks of gestations (risk of prematurity complications) in such cases ( intrauterine transfusion is teatment of choice ). In addition to serial Delta O.D. 450 value / wk , timing the delivery should be based on the patient's obstetric history and fetal well being ( non-stress test and biophysical profiles ) and lung maturity .
Liley chart
GA(WKS)
2- Cordocentesis : Other invasive investigation to determine fetal hematocrit value by using sample obtained from umbilical cord by U/S guided procedure also measure fetal blood gases , pH bilirbin levels .There is a risk FMH as high as 40% and tear in placental vessels may occur so it should not be a 1st line method of assessing fetal status & need experience .
In practice,the use of invasive tests to monitor disease progression(once a critical level has been reached) have been replaced by non-invasive assessment using MCA Doppler .
Transfusion in Rh iso- immunization ( either intra or extra-uterine )
Is life live saving in a severely anaemic fetus that is too premature for delivery to be contemplated.The aim is to restore Hb levels ,reversing or preventing hydrops or death.It will suppress fetal erythropoesis ,which reduces the concentration of antigen positive cells available for haemolysis. 1. Intrauterine transfusion ( either fetal intraperitoneal or intravascular ) : The goal is to transfer : fresh group O , Rh-ve densely packed red blood cells (Hb around 30 g/L), CMV-ve , washed , compatible to mother blood , irradiated blood ( to decrease the risk of graft versus host disease ) .
- Increase the survival rate ( to 85% 90% without hydrops ) & to ( 75% with hydrops ) .
A- Fetal intraperitoneal :
By placing blood in fetal peritoneal cavity where RBCs are absorbed in subdiaphragmatic lymphatic , ( the blood should be absorbed 7 to 9 days ) ( with presence of hydrops fetails the absorption will be delayed need aspiration of ascitis before transfusion ) or need other type of IU-transfusion ( intravascular transfusion ) may be the only option, for example in low gestations .
- The volume to be infused is basal on the following formula :
Volume = { GA ( wks ) 20 }* 10
Complication ( fetal bradycardia and sinusoidal pattern )
B- Intravascular transfusion :
needle inserted into the umbilical vein at the point of the cord insertion or intrahepatic vein or into the fetal heart .
The volume of blood to be transfused is based on the fetal weight ( as determined by U/S and concentration of donor blood . ( 30 50 ml/kg ) may repeated / wk till maturity of lung delivery .
Other methods of Management :
Maternal plasmaphoresis : may be helpful in severe erythropoiesis when intrauterine transfusion are not successful or no facilities for it available , can be done / wk to decrease maternal antibody levels .Phenobarbital : has been used to induce fetal hepatic enzymes activity , there by increasing uptake and excretion of bilirubin by the liver , Rx is initiated 2 to 3 wks before delivery .
New techniques for evaluation fetal Rh status :
Amnicocentesis : To test fetal blood types in cases of a heterozygous paternal genotype ( by polymerase chain reaction test ) .Fetal blood type by chorionic villous sampling ( but is discouraged because of potential for worsening fetal disease if fetus is Rh+ve .
Flow cytometry : has been successfully reported in sorting fetal cells from maternal blood ( DNA amplification using a single fetal nucleated erythrocyte can be used to determine fetal Rh D blood type .
Free fetal DNA in the maternal plasma or serum has also been utilized to detect Rh D sequences .
Mode of Delivery :
* If intervention is indicated > 35 wks gestation induction of labour ( if no contraindication for obstetric cause ) .* If < 32 wks C/S .
* There is a low threshold for C/S : because of :
1. avoid unsatisfactory or difficult labour .
2. anemic fetus is prone to fetal distress during labour , hypoxia and acidosis impair baby's to conjugate bilirubin .
* Allow most experienced neonatologist and lab personnel assembled to provide optimal treatment .
All babies born to Rhesus ve women should have cord blood taken at delivery for a blood count , blood group &indirect Coomb,s test .
Objective
The students should know about :
Management of sensitized Rh-ve pregnant .The non invasive methods for management .
The non invasive methods for the mamagment .
Liley graph and the queenan chart .
Type of intrauterine fetal transfusion .
New techniques for evaluation fetal Rh status .
Mode of delivery .