Rh Sensitization During Pregnancy - Topic Overview
If you are
Rh-negative, your red blood cells do not have a marker
called Rh factor on them. Rh-positive blood does have this marker. If your
blood mixes with Rh-positive blood, your
immune system will react to the Rh factor by making
antibodies to destroy it. This immune system response is called Rh
Rh sensitization can occur during pregnancy if you are
Rh-negative and pregnant with a developing baby (fetus) who has
Rh-positive blood. In most cases, your blood will not mix with your baby's
blood until delivery. It takes a while to make antibodies that can affect the
baby, so during your first pregnancy, the baby probably would not be
But if you get pregnant again with an Rh-positive baby, the
antibodies already in your blood could attack the baby's red blood cells. This
can cause the baby to have
jaundice, or more serious problems. This is called
Rh disease. The problems will tend to get worse with
each Rh-positive pregnancy you have.
Rh sensitization is one reason it's important to see your doctor
in the first trimester of pregnancy. It doesn't cause any warning symptoms, and
a blood test is the only way to know you have it or are at risk for it.
- If you are at risk, Rh sensitization can
almost always be prevented.
- If you are already sensitized,
treatment can help protect your baby.
Rh sensitization during pregnancy can only happen if a woman has
Rh-negative blood and only if her baby has Rh-positive blood.
- If the mother is Rh-negative and the father
is Rh-positive, there is a good chance the baby will have Rh-positive blood. Rh
sensitization can occur.
- If both parents have Rh-negative blood,
the baby will have Rh-negative blood. Since the mother's blood and the baby's
blood match, sensitization will not occur.
If you have Rh-negative blood, your doctor will probably treat
you as though the baby's blood is Rh-positive no matter what the father's blood
type is, just to be on the safe side.