What does a titer level of 1:4 for big k antibody mean in pregnancy?

Could be risky: Kell antibody comes from the mother having been exposed to Kell-positive blood either by blood transfusion, or by a previous pregnancy with a baby who has the Kell antigen (which the baby gets from the father). The Kell antibody can be very dangerous to the baby if the current baby is Kell-positive. You need to test this baby's father for his Kell antigen type (NOT antibody; antigen).