HemeOnc
Rh Sensitization
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Rh Sensitization
, Rh Isoimmunization
Pathophysiology
Maternal
Antibody
Formation to fetal Rh
IgM (Agglutinates in
Normal Saline
) forms in 7 days
Does not cross placenta
IgG (Agglutinates in Albumin) forms in 21 days
Crosses placenta easily
Results in
Hemolytic Disease of the Newborn
Neonatal
Hemolytic Anemia
Fetal hydrops
Indications for giving RhoGAM (xD) to Rh Negative Mother
Standard Timing
Week 28 gestation
Postpartum (under 3 days postpartum if baby Rh+)
Additional Indications
Placenta Separation
Labor Third Stage
Termination or
Spontaneous Abortion
after 6 weeks
Antepartum bleed
Abruptio Placenta
Abdominal Trauma
Procedures (Give
RhoGAM
within 72 hours of procedure)
Amniocentesis
or Cordocentesis
Chorionic Villus Sampling
External version
Dosing
Standard
RhoGAM
Dosing
Before 12 weeks gestation:
RhoGAM
50 mcg IM
RhoGAM
50 mcg IM has limited availability
Now
RhoGAM
300 mcg IM is given at this time
After 12 weeks gestation:
RhoGAM
300 mcg IM
First Trimester Bleeding
or
Late Pregnancy Bleeding
RhoGAM
dose based on
Kleihauer-Betke
Test
Labs
Rh Negative mother
Consider checking Rh type of father if paternity sure
Indirect Coombs
Test for Rh Antibodies
Identify specific antibodies
Titer may be weakly positive (1:4) from prior
RhoGAM
Titer > 1:8 dilution requires evaluation
Follow
Antibody
titer monthly
At Delivery: Test fetal blood
Maternal blood Sheep Rosette if fetus Rh positive
Sheep Rosette test results
Negative: Give 300 mcg
RhoGAM
Positive: Kleihauer Bettke based Rh vial numbers
Radiology
Fetal Ultrasound
: signs of
Fetal hydrops
Fetal
Ascites
Scalp edema
Amniocentesis
(replaced by MCA-PSV in most cases)
Obtain every 1-3 weeks when fetus > 26 weeks
Follow
Bilirubin
level in amniotic fluid
Liley Curve directs management per
Gestational age
Amniotic
Bilirubin
level >0.3 at 27 weeks gestation
Amniotic
Bilirubin
level >0.2 at 31 weeks gestation
Amniotic
Bilirubin
level >0.1 at 36 weeks gestation
Middle Cerebral Artery
Peak systolic velocity (MCA-PSV)
Best noninvasive marker for fetal
Hemoglobin
level
Depends on accurate gestation age
Reliable from 18-35 weeks
Interpreted on curve to determine severity
Genotyping
Determines if fetus at risk of Rh Sensitization
Previously required
Amniocentesis
Now cell free fetal DNA detected in maternal serum
Management (Based on severity evaluation above)
Neonatology
Consultation
Corticosteroid
s may be indicated
Phenobarbital may be indicated
Consider reducing maternal antibodies <18 weeks
Plasmapheresis of maternal serum or
Intravenous IgG
Consider early delivery (32-35 weeks)
Do not wait for
Fetal hydrops
Intrauterine transfusion via
Ultrasound
guidance
Indicated for severe cases based on testing above
Intravascular fetal transfusion via
Umbilicus
Intraperitoneal transfusion
Poorly absorbed in
Fetal hydrops
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