Transcript Red Cell Alloimmunization in Pregnancy

Michael McNamara, DO, FACOG
Sanford Maternal Fetal Medicine
Objectives
1. Understand the problem of red cell
alloimmunization during pregnancy
2. Diagnosis of red cell alloimmunization
3. Surveillance and treatment of patient
with red cell alloimmunization
 No
conflicts to disclose
 Maternal
immune system makes
antibodies against fetal red cell antigen
(paternal origin)
 Common etiology for immune hydrops
 Incidence 6.7/1000 (2002 data)
 Most commonly due to Rh disease, D
antigen
 Mom
exposed to foreign red cell antigen
• Fetal blood (paternal origin)
• Blood transfusion (most often Kell)
 Mom
develops antibodies
 Antibodies IgG or IgM
 IgG small enough to pass through
placenta
 Attacks (destroys) fetal red blood cells
 Fetal anemia, subsequent hydrops
Results in release of erythroblasts into fetal
circulation
 Increased cardiac output
 Tissue hypoxia
 Hydrops (fluid in two or more fetal
compartments)

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•
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
Ascites
Skin edema
Pleural effusions
Pericardial effusions
Polyhydramnios
Seen when fetal hemoglobin 7-10 g/dL below
normal
D
antigen on short arm of chromosome 1
 Absence (Rh-) homozygous
• 15% Caucasian European
• 30% Spanish from Basque region of Spain
• 8% African American, Hispanic (Mexican, South
American)
• < 1% native American, Eskimo, Chinese,
Japanese
Prevention of Alloimmunization
 Blood type incompatability
 Passive immunization
 300 ug protects against 30 ml fetal blood
 Given 28 weeks and following delivery (if
fetus Rh +)
 Quantify amount (Rhogam) based on
testing of amount of fetal blood in
maternal blood
 Maternal
antibody titers
 Fetus
 Ultrasound
 Degree
that Mom is responding to fetal
antigen
 Critical titer – titer with significant risk
for fetal hydrops
 Usually between 1:8 and 1:32 for D
antibodies
 Use same for other red cell antibodies
except Kell
 Paternal
testing
 Chorionic villus sampling
 Amniocentesis
 Cell free DNA
 Fetal blood typing
 Hydrops
– abnormal fluid in two or more
compartments
 Pleural effusion, pericardial effusion,
ascites, skin edema, polyhydramnios
 Doppler studies
• Middle cerebral artery (MCA)doppler studies
 Titers
checked monthly to 24 weeks, then
every two weeks for critical titer
 Once critical titer is reached (titers
checked monthly until 24 weeks and then
every 2 weeks) further evaluation
needed
 Amniocentesis
 Umbilical vein sampling
 Ultrasound
 Amniocentesis
(serial)
• Monitor bilirubin in amniotic fluid
• Amount (OD 450) vs gestational age
• Plot on Liley graph (curve) to see if fetus anemic
 Cord
Sampling
• 1-2% of fetal loss
• 50% chance for increasing hemolytic response
 Middle
cerebral artery Doppler blood
flow (MCA)
 Anemia increases blood flow (velocity),
less cells
 Plot the peak systolic velocity against
gestational age
 1.5 multiples of the median (MoM) or
greater suspect for fetal anemia, needing
fetal blood sampling, transfusion
 Non
invasive
 Sensitivity 88%
 Negative predictive value of 89%
 Identify
titer-1st episode usually no
consequence for fetus
 Paternal status / fetal status
 Titers monthly until 24 weeks, every two
weeks thereafter
 Critical titer – MCA Dopplers every 1-2
weeks
 Abnormal MCA – fetal umbilical vein
sampling, transfusion
High risk if previous pregnancy
 Fetal loss due to hydrops
 Fetal transfusion
 Neonatal exchange transfusion
 34
year old
 Gravid 2, para 1
 Presented in consult at 19+ weeks
 D antibody titer of 1:64
 Previous cesarean x 1
 Drug use history, currently on suboxone
 Fetus
with D antigen?
 Father not available for screening
 Normal anatomy except echogenic focus
in heart (soft marker for trisomy 21)
 Normal MCA Doppler
 Mom desired amniocentesis for
karyotype and assess fetal Rh status
 Normal
karyotype
 Fetal + D antigen
 Normal MCA doppler
 33+5
weeks
 Ultrasound showing elevated MCA peak
systolic velocity Doppler at 2.0 MoM
 Fetal ascites, polyhydramnios of 30.5 cm
Gestational Age
MCA
Doppler (MoM)
20+5
< 1.0
23+5
1.1
25+2
< 1.0
28+5
1.13
30+5
1.11
32+5
1.24
33+5
2.0
 Admitted, antenatal
steroids
 Delivery at 33+6 weeks repeat cesarean
 Earlier in pregnancy, consideration for
umbilical vein sampling and RBC
transfusion
 Uneventful post operative course