Rh incompatibility in pregnancy

lets us understand this with a case scenario:

a female with 28 weeks of gestation (POG) presented to you for follow-up. She is Rh-ve; Rh's status of her father is unknown because he is out of contact. At 8 weeks of POG, she had chorionic hematoma for which she received anti-D immunoglobulin. This time, her lab report says that her anti-D immunoglobulin status is negative. Does she require anti-D immunoglobulin this time?

Yes, she requires it now and postpartum as well.

when there was a chorionic hematoma, blood from the fetus entered the mother. To neutralize that, she received anti-D immunoglobulin. This time, her antibody status is negative means that she did not form much immunoglobulin against the exposed blood of the fetus. So, she requires again immunoglobulin at 28 weeks of gestation to protect her from future bleeding during delivery.

let us say, at this time, that her anti-D immunoglobulin status would have been positive which means there is no advantage of giving anti-D immunoglobulin now because she already has formed antibodies.

what test is done to determine whether antibodies are present in maternal serum?

This is called the rosette test. It is a qualitative test to determine whether there is fetomaternal hemorrhage.

Is there any quantitative test as well?

Yes, there is a quantitative test to determine the titer of the antibody, which is called kliheur betke test or flow cytometry.

why a quantitative test (why antibody titer) is done?

sometimes there is massive fetomaternal hemorrhage, therefore, in that condition, more than a normal dose of anti-D immunoglobulin might be required to neutralize fetal blood. Normally, 300mcg anti-D immunoglobulin neutralizes 30ml blood. 300mcg is a typical standard dose.

what are conditions where more than a normal dose of anti-D immunoglobulin is required?

Answer: abruption placenta because there is massive fetomaternal hemorrhage.


what are other conditions where anti-D immunoglobulin injection is required?

ectopic pregnancy, accidental abdominal trauma, chorionic villus sampling, amniocentesis, external cephalic version, Hydatidiform mole.


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