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 Rh blood type


What is "Rhesus (or Rh) Factor"?

Red blood cells are covered with many kinds of proteins and carbohydrate chains, a.k.a. "factors", which are determined by the genetic makeup of that person.  The different combinations produce the blood types, commonly known as the ABO types (A, B, AB, and O).  Most people, about 80% of the US population, have an additional factor called Rhesus.  They are Rh+.  Those without the Rh factor are Rh-.  So some people are A+, B-, AB+, O-, A-, B+, etc., for example.  When receiving donated blood, it is important that all the factors match or else the recipient's body will attack the donor blood.


Why does Rh Factor matter in pregnancy?

Just as a person with Type A blood cannot receive Type B blood, an Rh- person cannot receive Rh+ blood.  If this happens, the Rh- person will make antibodies to the Rhesus Factor and attack it.

During pregnancy, a baby's blood can mix with the mother's blood.  (This usually happens at the time of birth but can also happen during a traumatic accident, miscarriage, abortion, bleeding during pregnancy, or amniocentesis.)  If the baby is Rh+ and the mother is Rh-, then the mother will produce antibodies against her baby's blood type and attack the baby's blood.  These antibodies cross the placenta into the baby.  These antibodies remain in the mother's bloodstream for the rest of her life and will attack any future babies with an Rh+ blood type.  If, during the pregnancy, Rh antibodies are detected in the mother, the midwife will immediately refer her to specialized OB care for assessment and care as the baby will need extra monitoring and care at birth.

When both the mother and father of the baby have the Rh- blood type, the baby is going to be Rh- also so there is no chance of antibodies being made or attacking the baby.  If the mother is Rh+ and the father is Rh-, there is a 50-50 chance the baby will also be Rh-.


Hemolytic Disease of the Newborn  ("Heme" = red blood cells, "lysis" = breaking open)

When maternal Rh antibodies are produced (mom is Rh-, baby is Rh+), they can cross the placenta and attack the baby's red blood cells.  This causes abnormal development of the red blood cells, low oxygen delivery to the baby, and abnormal physical development.   Sometimes a baby is born relatively unaffected, sometimes he is born prematurely and needs a blood transfusion, and sometimes a stillbirth or miscarriage occurs.

The first transfer of baby blood to the mother usually occurs during the birth of the first child.  At this point, the mother's body starts making antibodies and the first child is completely unaffected.  By the time the next pregnancy occurs, there are higher levels of circulating antibodies.  This baby is likely to be affected from early in the pregnancy.  This is why the severity of the disease generally increases with each pregnancy.



There is no way to prevent an Rh- blood type.  What we do have today is a medication called "Rh Immunoglobulin" that helps prevent the Rh- mother from making antibodies.  It works by attaching to the baby's Rh+ red blood cells and "hiding" the fact that they are Rh+ until they die and become inactive.  An injection of the medication is given to the mother at 28 weeks gestation and within 72 hours of birth, generally.  There are several trade names for Rh Immunoglobulin, the most well-known is Rhogam.

What to know about the Rh Immunoglobulin


You should not receive it if you are Rh+!

This medication is a blood product made from a pooled sample.  This means that the blood or plasma of many people is pooled together during the production process.  Although very high standards are met to prevent contamination of the medication with viruses or bacteria, this possibility cannot be excluded.  Some women are uncomfortable with this.  It also contains preservatives. It costs between $75 and $200 per shot, depending on the availability, brand, and insurance coverage.  However, insurance does cover it (at least partially).  It can cause side effects such as soreness, allergic response, fever, chills, and headache, but they do not usually last long.

You should not receive it if you have had a previous allergic response to Rh Immunoglobulin or other human blood products, or if you have a problem with IgA production.

There has been no conclusive research to show that there is an effective alternative to the Rh Immunoglobulin for the prevention of hemolytic disease in the newborn.  However, some women feel that they can safely forego the prenatal dose (at 28 weeks) and accept only the postpartum dose.  Some women feel that the risk of having baby's blood mix in theirs is reduced by the gentle birth practices of midwives.


The medication is available from your midwife who buys it from the drug company.  She will also administer it.  Rhogam is usually paid by your insurance company. If you do not have insurance payment will need to be be paid prior to use.


Remember that neither the Rh Immunoglobulin or alternative therapy can guarantee that the mother will not be sensitized to the baby's Rh+ blood type.


Special attention from your midwife

If you are Rh-, the first question to answer is: what blood type does the baby's father have?  If he is Rh-, then there is no need for any medication prenatally or postpartum (but we do need documentation of his blood type for the chart).  Some women choose to have the baby's blood typed at birth, in order to determine the need for the postpartum dose of medication.   You can decide for yourself what course of treatment you want.







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