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Management of Rh alloimmunization

CDE (Rhesus) System Includes c, C, D, e, E D negativity defined as absence of D antigen

Antibodies Associated with Anti-c, Anti-D, Anti-E, and Anti-Kell Anti-D-immunoglobulin prophylaxis reduced the hemolytic disease caused by anti-D, but not the others

Minor RBC Antigens causes hemolyisis Kell is most common of minor Responsible for 10% of cases of severe antibody-mediated anemia **Transfuse women with Kell(-) blood**

Inert Antibodies Antigens such as A, P, Le (a), M, I, IH, and Sd (a) are innocuous Mostly are IgM Lewis antibodies is the commonest one detected

Sensitization rate 16 percent without prophylaxis 2 percent with routine postpartum administration 0.1 percent with routine antenatal administration

Causes of Rh isoimmunization Delivery Induced abortion Spontaneous abortion Ectopic pregnancy Partial molar pregnancy Chorionic villus sampling Cordocentesis

Amniocentesis External cephalic version Abruptio placenta Antenatal hemorrhage Maternal abdominal trauma Spontaneous Needles Blood and blood product

Clinical Management Routine booking blood group &Antibodies screen Rh –v Ab –v Determine father’s RhBC status if -v No risk

If the father is +ve for-D-antigen, fetus is at RISK - Repeat Antibodies screen at 28 weeks for Rh-ve women prior to receiving Anti-D immunoglobulin -Determine father’s RBC antigen status and zygosity

Clinical Management If Antibody screen is +ve, identify antibody type Identify the risk factors for alloimmunization (past pregnancies, transfusions, shared needles)

Clinical Management Obtain antibody titer from the mother if the past history is not significant for an affected pregnancy. **Titers less reliable after a sensitized pregnancy** Consider invasive testing at titer of 1:16 or greater by indirect Coombs

Clinical Management If Antibodies titer remains below critical titer- invasive testing is not indicated and the patient can be followed up by serial Antibodies titter Serial titers before 18-20 weeks not necessary

If Antibodies titer is above the critical level or the past history is positive regardless of the antibodies titer - invasive testing is indicated

Clinical Management Amniocentesis for amniocytes at 15 weeks by (PCR) to determine fetal blood type if father is heterozygous. Free fetal DNA in maternal circulation.

Fetal antigenic determination Amniocentesis, CVS, cordocentesis samples can be used to determine fetal antigen status by DNA typing 100% accuracy in 390 samples Bennett et al. 1993 Molecular analysis of maternal plasma: fetal DNA for RhD 100% accuracy in 45 fetuses second/third trimester Lo et al. N Engl J Med 1998;339:1734-8.

Possible utility in embryo selection for sensitized mothers PCR from cell free DNA in maternal serum 100% accuracy in 137 fetuses (including 21 female fetuses) Finning et al. Transfusion 2002;42:1079-85. Possible utility in embryo selection for sensitized mothers

Clinical Management Serial amnio to measure delta OD450 and plot values on Liley or Queenan graph

Delta OD450 Spectral analysis of amniotic fluid at 450 nm proposed in 1961 by Liley- measures change in OD Measures the level of bilirubin and predicts severity of hemolytic disease after 27 weeks Delivery or intrauterine transfusion if delta OD450 falls into zone III or upper zone II

Queenan Curve Proposed another method of using delta OD450 Suggested four zones and extended the gestational age to 14 weeks

Limitations of Amniocentesis May give a falsely elevated bilirubin level in presence of mec or blood May be low after exposure to light or in Kell alloimmunization

Cordocentesis Gold standard for detection of fetal anemia Complications! 2.7% total risk of fetal loss Reserved for patients with increased MCA-PSV or delta OD450

MCA-PSV Velocity of blood flow in brain increased with anemia 1. Increased cardiac output 2. Vasodilatation in the brain 3. Decreased blood viscosity

MCA & FETAL ANEMIA The MCA PSV correlated well with hematocrit and hemoglobin concentrations and is useful for predicting the severity of fetal anemia (Mari G. 1995) The MCA PSV increases in fetuses with anemia (Roberts AB. 2001)

FETAL ANEMIA Fetal anemia  blood viscosity  Cardiac output peripheral vasodilatation  Blood flow to the Brain, Heart and Adrenal gland Mari G. 1990 Many A. 1996 HecherK. 1995 Bahauddin Sallout

Correct Technique for MCA Doppler Fetus resting Circle of Willis imaged in axial image using color Doppler Entire length of MCA Close to origin of internal carotid artery

MCA LOCALIZATION In a transverse axial view of the fetal head at a slightly more caudal plane than the one used for BPD At this level, which include the cerebral peduncles, the MCA can be seen as a major lateral branch of the circle of Willis Bahauddin Sallout

MIDDLE CEREBRAL ARTERY Transverse view of the fetal head with color Doppler showing the circle of Willis Flow velocity waveforms from the MCA at 32 wk

MIDDLE CEREBRAL ARTERY Normal flow in 1º trimester Normal flow in 2º & 3º trimester

MCA-PSV I would like to review our technique for measuring the middle cerebral artery peak systolic velocity, using the following steps: Identification of the circle of Willis by color Doppler on an axial section of the brain slightly superior to the thalami and cavum septum pellucidum. Then, identification of the middle cerebral arteries flowing anteriorly and outward; just behind the orbits. The sample volume line is placed as close as possible to 0 degrees; parallel to the walls of the vessel, in the proximal middle cerebral artery, close to its origin but not incorporating the internal carotid artery. The middle cerebral artery peak systolic velocity is then measured at the highest point of the Doppler waveform. The MCA-PSV is measured multiple times and the highest peak systolic velocity is recorded.

MCA & FETAL ANEMIA Fetal anemia due to maternal alloimmunization Bahauddin Sallout

MCA ABSENT DIASTOLIC FLOW Severe hydrops (kell antibody) Bahauddin Sallout

Rh Alloimmunization management If using MCA-PSV, and initial is less than 1.5 MoM, weekly testing Cordocentesis or delivery depends on the gestational age once the MCA-PSV reaches 1.5 MoM

Several prospective studies have found that elevated middle cerebral artery peak systolic velocities as measured by Doppler ultrasonography correlate with the presence of fetal anemia in alloimmunized pregnancies. Work by Mari et al., published in 1995, - not only correlated elevations in middle cerebral artery peak systolic velocities with fetal anemia, but also established a nomogram for the normal range of middle cerebral artery peak systolic velocity as a function of gestational age. Mari et al. N Eng J Med 2000

Advantages of MCA-PSV Non-invasive Mother not put at risk for worsening alloimmunization Can be used with all antibodies other than RhD, including anti-Kell antibodies

Disadvantages of MCA-PSV Need skill Done weekly Accuracy decreases after 35 weeks False +ve results 12 percent

Current evidence supporting MCA-PSV Doppler velocimetry Initial prospective study of 16 fetuses: 14 anti-D, 2 anti-c Mari et al. Ultrasound Obstet Gynecol 1995;5:400-5. Since then several prospective and retrospective studies: over 200 additional cases Rbc alloimmunization and parvovirus B19 1-Scott et al. Prenat Diagn 1998;18:1143-8. 2-Teixeira et al. Ultrasound Obstet Gynecol 2000;15:205-8. 3-Delle Chiaie et al. Ultrasound Obstet Gynecol 2001;18:232-6. 4-Mari et al. N Eng J Med 2000;342:9-14. 5-Zimmermann et al. Br J Obstet Gynecol 2002;109:746-52. 6-Mari et al. Ultrasound Obstet Gynecol 2002;99:589-93.

Current evidence supporting MCA-PSV Doppler velocimetry Sensitivity 87-90% Specificity 88-100% PPV 53-74% NPV 98-100% Data combined from 7 studies: rbc alloimmunization and parvovirus B19

Prediction of fetal anemia by MCA-PSV Doppler compared to Amniocentesis 4 Comparative Studies N = 28 Nishie EN, et al. Am J Obstet Gynecol 2003;188:214-9 N = 28 Pereira L et al. Am J Obstet Gynecol 2003;189:1002-6 N = 38 Bullock ,et al. Ultrasound Obstet Gynecol 2005 N = 165 Oepkes D, et al. N Engl J Med 2006;355:156-64.

Current evidence MCA-PSV Doppler Amniocentesis Sensitivity 53-86 64-100 Specificity 71-78 81-91 PPV 44-100 47-75 NPV 95-96 97-100 N =259 Cumulative ranges from 4 trials

Conclusion MCA-PSV accurately predicted moderate to severe fetal anemia Compared to conventional management, MCA-PSV may have a better predictive accuracy for moderate or severe anemia in alloimmunization Management by MCA-PSV may eliminate the need for amniocentesis and reduce the number of PUBS performed in alloimmunized pregnancies

Potential Benefits of Management by MCA-PSV 14,000 cases of alloimmunization per year in the U.S. Avoid 24,500 amniocenteses and 900 PUBS Avoid 1 pregnancy loss/preterm delivery for every 100 patients; 142 nationwide per year Avoid worsening sensitization from procedure related bleeding complications – TPH risk 2-10% following amniocentesis, 50% following PUBS It is possible that management with MCA-PSV Doppler will reduce the number of invasive procedures and minimize procedure related losses. In the U.S there are approximately 14,000 cases of alloimmunization annually. If we applied the trend we observed to the U.S population, we could avoid 24,500 amniocenteses and 980 PUBS per year by using MCA-PSV. With a complication rate of 0.5% for amniocentesis and a conservative estimate of 2% for PUBS you would avoid 1 pregnancy loss or preterm delivery per 100 patients (over 140 annually) using MCA-PSV over conventional management - and these would likely occur in a mildly anemic or non-anemic fetuses. Furthermore, an additional benefit would occur from avoiding procedure related bleeding complications which increase sensitization and worsen disease.

Prevention of Alloimmunization Doses of ani-D-immuonoglubuline for Rh-ve) 50 mcg dose protects against 2.5 ml of Rh (+) RBC’s 300 mcg dose protects against 15 ml of RBC’s or 30 ml of Rh (+) blood 20 mcg per ml RBC

Prevention standard recommendations 300 mcg dose within 72 hrs of delivery to unsensitized Rh (-) women (Rh positive infant) 13 days , 28 days 300 mcg at 28 weeks UNLESS father known to be Rh (-) Repeat Antibody Screen before giving the prophylactic dose?

Indications for administration of anti-(D) immune globulin At 28 weeks of gestation Spontaneous abortion, threatened abortion, induced abortion Ectopic pregnancy Invasive procedures: genetic amniocentesis; chorionic villus sampling; multi-fetal reduction; fetal blood sampling Hydatidiform mole

Fetal death in the second or third trimester Blunt trauma to the abdomen Antepartum hemorrhage in the second or third trimester (eg, placenta previa or abruption) External cephalic version

Prevention Test for excessive fetal-maternal hemorrhage after blunt trauma, abruption, cordocentesis, and bleeding assoc. with previa Kleihauer Betke

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