Objectives

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Management of Rh alloimmunization
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CDE (Rhesus) System

• Includes c, C, D, e, E
• D negativity defined as absence of D antigen

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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

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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

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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

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Sensitization rate

• 16 percent without prophylaxis
• 2 percent with routine postpartum
  administration
• 0.1 percent with routine antenatal administration

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Causes of Rh isoimmunization

• Delivery
• Induced abortion
• Spontaneous abortion
• Ectopic pregnancy
• Partial molar pregnancy
• Chorionic villus sampling
• Cordocentesis

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

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Clinical Management

• Routine booking blood group Antibodies screen
• Rh v Ab v
• Determine fathers RhBC status if
• -v No risk

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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 fathers RBC antigen status and
zygosity
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Clinical Management

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

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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 116 or
  greater by indirect Coombs

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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

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

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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 19983391734-8.
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PCR from cell free DNA in maternal serum 100
accuracy in 137 fetuses (including 21 female
fetuses) Finning et al. Transfusion
2002421079-85. Possible utility in embryo
selection for sensitized mothers
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Clinical Management

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

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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

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Queenan Curve

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

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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

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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

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MCA-PSV

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

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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)

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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
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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

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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

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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

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MIDDLE CEREBRAL ARTERY

• Normal flow in 1º trimester
• Normal flow in 2º 3º trimester

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MCA-PSV
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MCA FETAL ANEMIA

• Fetal anemia due to maternal alloimmunization

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MCA ABSENT DIASTOLIC FLOW

• Severe hydrops (kell antibody)

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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

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Mari et al. N Eng J Med 2000
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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

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Disadvantages of MCA-PSV

• Need skill
• Done weekly
• Accuracy decreases after 35 weeks
• False ve results 12 percent

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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 19955400-5. Since then several
prospective and retrospective studies over 200
additional cases Rbc alloimmunization and
parvovirus B19 1-Scott et al. Prenat Diagn
1998181143-8. 2-Teixeira et al. Ultrasound
Obstet Gynecol 200015205-8. 3-Delle Chiaie
et al. Ultrasound Obstet Gynecol
200118232-6. 4-Mari et al. N Eng J Med
20003429-14. 5-Zimmermann et al. Br J
Obstet Gynecol 2002109746-52. 6-Mari et al.
Ultrasound Obstet Gynecol 200299589-93.
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Current evidence supporting MCA-PSV Doppler
velocimetry
Sensitivity 87-90 Specificity 88-100 PP
V 53-74 NPV 98-100 Data combined from 7
studies rbc alloimmunization and parvovirus B19
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Prediction of fetal anemia by MCA-PSV Doppler
compared to Amniocentesis
4 Comparative Studies N 28 Nishie EN, et
al. Am J Obstet Gynecol 2003188214-9 N
28 Pereira L et al. Am J Obstet Gynecol
20031891002-6 N 38 Bullock ,et al.
Ultrasound Obstet Gynecol 2005 N 165 Oepkes
D, et al. N Engl J Med 2006355156-64.
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Current evidence
MCA-PSV Doppler
Amniocentesis
Sensitivity 53-86 64-100 Specificity 71-7
8 81-91 PPV 44-100 47-75 NPV 95-96 9
7-100
N 259 Cumulative ranges from 4 trials
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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
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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

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Prevention of Alloimmunization

• Doses of ani-D-immuonoglubuline for Rh-ve)
• 50 mcg dose protects against 2.5 ml of Rh ()
  RBCs
• 300 mcg dose protects against 15 ml of RBCs or
  30 ml of Rh () blood
• 20 mcg per ml RBC

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Preventionstandard 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?

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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
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• 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

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Prevention

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

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Thank you