Togivel Page 448 - the best algorithm for management of Rh negative sensitized mother

25% of fetuses from D-alloimmunized pregnancies will have mild-to-moderate hemolytic anemia and 25% of them will develop hydrops.
- Positive titre: Each laboratory sets its own positive titer for anti-D antibody that requires follow-up.
- Threshold titre: correlates with a moderate risk of HDFN.
Referral for a fetal medicine opinion should therefore be made in addition to follow up.
- Critical titer this is the titer at which fetal hydrops is likely to occur. Assessment of severity of anemia should be made.

Identifying fetuses at risk of fetal anemia –Rh +ve fetus- and:
Rising antibody levels/titres.
Specific Antibody Level above a THRESHOLD TITRE
- once anti-D levels are More than 4 iu/ml .
- once anti-c levels are More than 7.5 iu/ml.
- For anti-K antibodies, referral should take place once detected, as severe fetal anaemia can occur even with low titres.
- The presence of anti-E potentiates the severity of fetal anaemia due to anti-c antibodies so that referral at lower levels/titres is indicated.

Identifying fetuses at risk of severe fetal anemia –Rh +ve fetus- and:
1- CRITICAL TITRE is reached.
once anti-D levels are More than 15 iu/ml .
once anti-c levels are More than 20 iu/ml.
once anti-c levels are More than 7.5 iu/ml in presence of Anti-E antibodies
anti-K antibodies, any titre.
2- Ultrasound features suggestive of fetal anaemia/Hydrops.
3- History of unexplained severe neonatal jaundice, neonatal anaemia requiring transfusion or exchange transfusion.

In cases of fetuses at risk of SEVERE fetal anemia
Next step is Diagnosis of severe fetal anemia, can be done by:
Non-invasive Ultrasound doppler assessment of Middle cerebral artery peak systolic velocity value expressed as Multiples of the median (more than 1.5 MoM = Severe anemia).
Invasive Amniocentesis Amnionic Fluid Spectral Analysis this is largely replaced now by MCA-PSV

In cases of severe anemia diagnosed by assessment (MCA-PSV 1.5 MoM)
 Next step is to diagnose the possible need for intervention (Intrauterine fetal blood transfusion or delivery) can be done by:
Cordocentesis fetal blood sampling and measurement of fetal hematocrit.
In cases of cordocentesis verifying fetal Hct below 30% = Treatment indicated by:
Intrauterine blood transfusion ( before 35 weeks), or
Induction of labor (after 35 weeks).
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