Hello and thank you for asking HCM,
it is possoble that your child is negative because someone who is "Rh positive" has a
genotype either Rh+/Rh+ or Rh+/Rh-. Someone who Rh- has a genotype of Rh-/Rh-. So the child has inherited one negative allel of you and one from his father.
If you are Rh-negative, you may developed
antibodies to your Rh-positive child. If a small amount of the baby’s blood mixes with your blood, which often happens, your body may respond as if it were allergic to the baby. Your body may make antibodies to the Rh antigens in the baby’s blood. This means you have become sensitized and your antibodies can cross the placenta and attack your baby’s blood. I will wright you down the treatment for
RH negative mothers.
If a woman with Rh-negative blood has not been sensitized, her doctor may suggest that she receive RhIg around the 28th week of
pregnancy to prevent sensitization for the rest of pregnancy.
If the baby is born with Rh-positive blood, the mother should be given another dose of RhIg to prevent her from making antibodies to the Rh-positive cells she may have received from their baby before and during delivery.
The treatment of RhIg is only good for the pregnancy in which it is given. Each pregnancy and delivery of an Rh-positive child requires repeat doses of RhIg.
Rh-negative women should also receive treatment after any
miscarriage, ectopic pregnancy, or induced
abortion to prevent any chance of the woman developing antibodies that would attack a future Rh-positive baby.
I hope this asnwer was helpful to you.