Rh Sensitization
Rh Sensitization
In addition to the letter that signifies your blood type (A, B, AB, or O), there is also a positive or negative Rh factor that determines your true blood type. Most people are Rh positive, but being Rh negative does not affect your health in any way. In fact, the only time you need to worry about your Rh factor is when you or your partner is pregnant.
A mother is at risk of Rh sensitization if she is Rh negative and the father is Rh positive. In this instance, the fetus may be Rh positive. If for some reason during the pregnancy the baby's blood is mixed in with the mother's, she may begin to create antibodies to fight off the positive Rh factor. To put it simply, the baby's blood introduces something foreign into the mother's blood, and the mother's body creates antibodies to fight the Rh protein.
Sensitization can occur anytime an Rh positive baby's blood passes to an Rh negative mother's system through regular delivery, miscarriage, abortion, ectopic pregnancy, amniocentesis, or blood transfusion. Rarely will this cause a problem with a first pregnancy, but it can lead to problems in any future pregnancy.
In order to prevent antibodies from forming, Rh negative mothers are given a shot any time there is bleeding during the pregnancy. This injection, usually referred to as Rhogam, suppresses her body's ability to react to the Rh positive blood cells. The shots are effective for approximately 12 weeks so they are normally given around the 28th week of pregnancy to prevent problems from occurring during delivery. Rhogam will also be given after delivery if the baby's blood tests reveal he or she is Rh positive.
Though healthcare professionals take great care to protect Rh negative mothers from becoming sensitized, there are times when Rhogam may not have been delivered at the proper time or was ineffective. These instances are rare, but they do sometimes lead to sensitization.
Should a sensitized mother become pregnant again, her doctor will monitor her and the fetus closely for signs of hemolytic disease. If hemolytic disease is present, it means that the mother's antibodies have gotten into the baby's system and are trying to attack the positive Rh factor in the baby's blood. This breaks down the baby's red blood cells, often causing anemia. Many times the baby is only affected minimally and can be delivered in a normal and healthy manner. In severe cases, hemolytic disease may require the baby to be delivered early. The baby may need a blood transfusion in utero or shortly after birth.
In almost all cases where the baby was treated for hemolytic disease, either before or after birth, they experience few complications. Some may require photo treatment to lessen excess bilirubin, which is similar to the treatment many infants receive for jaundice.
It is important to let your caregiver know if you are Rh negative, and if you have had an Rh positive baby in the past. Any bleeding during pregnancy, no matter how little, should be brought to your practitioner's attention, as it may cause problems with Rh sensitization.
