Prevention of Rh Alloimmunization Flashcards
Reasons you might have commingling of blood between mom and fetus
spontaneously miscarriage ectopic pregnancy ante natal bleeding ECV delivery amniocentesis cvs
how do problems happen with alloimmunication
- patient makes antibodies
- antibodies cross the placenta
- these destroy fetal RBCs, causing various degrees of fetal anemia
- 0.1cc blood commingling is enough to create a problem
How do you prevent problems
- Give Anti-D antibody
- 300ug at 28w (covers silent spontaneous maternal- fetal transfusions
- during delivery if baby is Rh positive, then KB test or flow cytometry should be done to assess for how much rhogam is needed
if Rh neg over is found to have antibodies…
- still should get rhogam if the anti-D immunoglobulin. are deemed to be passive consequent due to recent administration of rhogam
- if deemed to be actively generated (natural immune mediate response), administration will not be effective
FOB status
- 3% non-paternity
- therefore all women should be treated regardless of paternal status
Weak D
= partial expression of D antigen
- can still develop antiD antibodies to that portion of the D antigen which they do NOT possess, they can still cause iso-immunization of an Rh- positive baby
- these women should be treated like they are negative
- they should get Rhogam
- if these pt’s donate blood, they are treated at Rh+ blood (cause they have some expression)
threatened AB <12w
- lack of data, no recommendation offered
- some give 50 ug dose
- molar pregnancy
- yes should get rhogam
surgical or medical abortion <12w
surgical or medical ectopic pregnancy
50 ug of rhogam
(300 ug after 12w)
Goes up because increasing RBC volume
trauma
should give Rhogam and KB test to determine how much
ante natal hemorrhage
KB to determine how much rhogam
screening recommended at
28w
rhogam is good for
3 weeks
If doesn’t get it pp
still give it at 28d follow up appointment, may still have benefit
Rh basic screening program
- non-sensitized women should get anti-D immunoglobulin at 28w and within 72h of birth if neonate confirmed positive (KB test needed to determine how much
Antibodies that cause fetal hemolysis
- Marked
- Mild
Marked
- Kell (K1)
- RhD
- Rhc (small c)
Mild
- Duffy
- Kidd
- RhC
- RhE
- Rhe
Amount of Rhogam needed
- 300 mcg for sig bleeding or invasive procedure (72h-28d)
- 300 mcg covers 30 ml fetal whole blood, 15 of RBC
- Give 300 mcg at 28 ppx
- delivery give 300, KB to determine if need more (0.3% deliveries)
- If protocols not followed, 17% will get alloimmunized (not 100%)
Management of Alloimmunnzation in pregnancy
First pregnancy/Current
First pregnancy = mild disease
Follow maternal titers if titer is 8 or less
- – <24w, monthly titers
- – >24w, q2w titers
Critical titer: 8-32
- – risk of hydrops
- – begin MCA dopplers (looking for fetal anemia)
- – note Kell titers not predictive of fetal status
MCA dopplers protocol
- q1-2w
- MCA > 1.5 MoM – PUBS, possible IUT
- IUT threshold often fetal Hct 30%
Paternity and alloimmunization
Generally not trusted
FOB positive (hetero)
- 50% chance fetus at risk for hemolyic disease
- Can test fetus through sfDNA (if RhD)
- Amnio for all other types
FOB positive (homo)
- 100% change fetus at risk for hemolytic disease
- Needs MCA doppplers
Alloimmunization
Second pregnancy
Titers nto predictive
FOB hetero
- Get fetal status (cfDNA if RhD, amnio otherwise)
FOB homo
- MCA dopplers start at 18w
