What is the most likely explanation for a weakly positive DAT in a B-positive baby born to an O-negative mother?

What is the most likely explanation for a weakly positive DAT in a B-positive baby born to an O-negative mother?

• A. Technical error
• B. A low titer anti-D
• C. Immune anti-B from the mother
• D. A maternal antibody against a low-incidence antigen

Answer: (C)

In this scenario, the presence of a weakly positive Direct Antiglobulin Test (DAT) in a B-positive baby born to an O-negative mother can be primarily attributed to the maternal immune response. Given that the mother is blood type O, she naturally produces anti-A and anti-B antibodies. In this case, the baby being type B means that it has inherited the B antigen from the father, while the mother’s immune system recognizes the B antigen as foreign and could produce low levels of anti-B antibodies. These maternal anti-B antibodies can cross the placenta and bind to the B-antigen on the fetal red blood cells, leading to a weakly positive DAT result. This is a typical situation where the mother's antibodies affect the baby's blood type, particularly in cases where the mother has antibodies against antigens present in the child’s blood type. In contrast, the other options involve factors that wouldn’t account for the observed weakly positive DAT in this specific context. A technical error would not lead to a consistent weakly positive result. A low titer anti-D wouldn’t be applicable here, considering that the mother is Rh-negative, and therefore the likelihood of anti-D antibodies affecting the baby is minimal. Lastly, a maternal antibody against a low

In this scenario, the presence of a weakly positive Direct Antiglobulin Test (DAT) in a B-positive baby born to an O-negative mother can be primarily attributed to the maternal immune response. Given that the mother is blood type O, she naturally produces anti-A and anti-B antibodies. In this case, the baby being type B means that it has inherited the B antigen from the father, while the mother’s immune system recognizes the B antigen as foreign and could produce low levels of anti-B antibodies.

These maternal anti-B antibodies can cross the placenta and bind to the B-antigen on the fetal red blood cells, leading to a weakly positive DAT result. This is a typical situation where the mother's antibodies affect the baby's blood type, particularly in cases where the mother has antibodies against antigens present in the child’s blood type.

In contrast, the other options involve factors that wouldn’t account for the observed weakly positive DAT in this specific context. A technical error would not lead to a consistent weakly positive result. A low titer anti-D wouldn’t be applicable here, considering that the mother is Rh-negative, and therefore the likelihood of anti-D antibodies affecting the baby is minimal. Lastly, a maternal antibody against a low