Pre delivery screen on Mom= O Neg with a negative IAT(confirmed with a repeat on another sample).

Baby= A Neg, DAT=Neg(with anti IgG), IAT=Pos on baby, D neg screen cells from panel=neg.

It is presumed that that pos IAT on the baby is from antenatal RhIG that was given to Mom, but why is Mom's IAT negative?

Half life of IgG is ~27 days AND a lot has probably crossed the placenta out of the mom's circualtion . . . would be my guess.

We see this several times a year. I agree with David, a lot has crossed the placenta.

JB

Silly question - why ever are you doing an antibody screen on the baby's plasma when the DAT is negative and, I presume, the baby is healthy?

Anna

I agree with David and Joan (and Anna).

Many years ago, Prof Jack Hobbs showed that the concentration of antibody in the baby (whether a true maternal antibody or an antibody injected into the mum) is greater than that in the circulation of the mum. This is because of active transport across the placenta. But why do the test in the first place if the baby is fit and well?

We will perform an antibody screen on baby (not mom) as part of the pretransfusion testing.

We will perform an antibody screen on baby (not mom) as part of the pretransfusion testing.

A baby will only have maternal antibodies at birth so an antibody screen (and reverse group) are not necessary. The group should be done on cord blood and any crossmatches should be done against the mother's plasma/serum for newborns.

Edited December 2, 201113 yr by Auntie-D

A baby will only have maternal antibodies at birth so an antibody screen (and reverse group) are not necessary. The group should be done on cord blood and any crossmatches should be done against the mother's plasma/serum for newborns.

Don't believe everything you read in books! Although, I would agree, that an antibody screen is unnecessary, as any "immune" antibodies are going to be maternal, some precocious babies will be born with their own anti-A and/or anti-B, and this has been proved by performing Gm and Km typing (different Gm and/or Km type than the mother).