What is Rh Negative Blood Grouping?
Why use RhoGAM?
What happens when there is blood mixing?

I often received requests from Rh Negative clients to explain the  Rh Negative blood grouping and the use of Rho Gam.  Why would they  consider  using it?   What  are  the potential  effects if they didn't  and there was a  substantial  amount  of  blood mixing during birth?   I composed the following information to help shed a little more clarity on this complex topic.  ~Susan Oshel~

Are You Rh NEGATIVE?
Rh Blood Grouping

A Little History
 

The Rh blood grouing was originally discovered in1940 by Karl Landsteiner and Alexander Wiener.  They discovered it on the surface of erythrocytes of the rhesus monkey while researching how to make the antiserum for typing blood  samples.  Thus the name "Rhesus" or "Rh" for short.   This was 40 years after Landsteiner had discovered the ABO blood groups.  Over the last half century, we have learned far more about  the  processes  responsible for Rh types.  They discovered that  it was indeed present in the human population.  When the Rh blood group is present on the surface of the red blood cells,  an individual’s blood type is designated Rh (+), when the Rh blood group is absent, the blood type is Rh (-).  If an individual with Rh (-) blood receives a transfusion of Rh (+) blood,  it causes the formation of anti-Rh agglutinin.  Subsequent transfusions of  Rh (+) blood may result in serious transfusion reactions  (agglutination and hemolysis of red blood cells).  A pregnant  woman who is Rh (-) may become sensitized  (receiving a transfusion of Rh (+) blood)  from the Rh (+) baby within her  womb.  She would then produce Rh antibodies.  In subsequent pregnancies,  if the baby is Rh (+),  Rh antibodies  produced  in  the maternal blood may cross the placenta and destroy fetal cells, giving rise to erythroblastosis fetalis; hemolytic disease of the newborn.  In the United States, 1 out of 1000 babies are born with this condition.

Rh type mother-fetal incompatibility occurs onlywhen an Rh (+) man fathers a child with an Rh (-) mother.  Rh incompatibility develops when an Rh (-) mother carries an  Rh (+) baby.  When fetal red blood cells cross the placenta and enter the mother's blood stream, they stimulate maternal antibody production against the Rh factor.  These antibodies then in turn cross the placenta back into the same baby if  the blood mixing happened during that baby's pregnancy,  or into a future baby if the blood mixing happened during the birth process.  Rh incompatibility can result in profound anemia in the unborn baby, causing death in the womb or after birth.

An infant who has been sensitized with the Rh isoimmunization should be treated as immediately as possible by a physician who is capable of, and has the facilities and blood supplies available for, exchange transfusions.

The use of Rh(D) immune globulin (trade name: RhoGAM) has been of great benefit in preventing sensitization of an Rh (-) mother by an Rh (+) baby, thus preventing hemolytic disease of the newborn in a future pregnancy, administered within 72 hours after birth.  It is derived from the plasma of a person with high levels of Rh antibodies. It is a solution of gamma globulin containing anti-Rh.  It acts to prevent and suppress the Rh immune response in the mother before she reacts to (or) builds antibodies to the foreign blood group in her system.  In other words,  it removes the positive blood from her bloodstream by apheresis before antibodies form.

An excellent educational Rh Factor site: http://www.biology.arizona.edu/human_bio/problem_sets/blood_types/rh_factor.html

ERYTHROBLASTOSIS FETALIS
The Baby's Risk

Erythroblastosis Fetalis is a hemolytic disease of the newborn as a result of maternal-fetal blood group incompatibility, specifically involving the Rh factor and less specifically the ABO blood groups.  It is also referred to as “hydrops fetalis".

The condition is caused by an antigen-antibody reaction in the blood stream  of  the  infant  resulting from the placental transmission of the mother's previously formed antibodies against the incompatible antigens of the baby's Rh(+) blood.

In  the  Rh factor incompatibility,   the  hemolytic  reaction  occurs  only  when  the  mother  is  Rh (-)  and the baby is  Rh (+). Maternal sensitization can be prevented  by injection of a high-titer anti-Rh gamma globulin preparation after  delivery.    No sensitization  can  occur  in  situations  in  which a strong placental barrier  prevents transfer of fetal blood into  the  maternal circulation. That is the case in most births. Blood mixing is not a normal  condition of birth.  Partial separation of the placenta with bleeding before it delivers is the usual way that fetal blood mixes with maternal blood during delivery.

Clinical manifestations of erythroblastosis fetalis include severe anemia, jaundice, enlargement of the liver and spleen; which without   intervention   can  lead  to  hypoxia,    cardiac  failure,   respiratory  distress  and  death.   Treatment  includes  blood transfusions until the baby's blood and symptoms stabilize.

RhoGAM

RhoGAM became available after the 1950's. In the past,  before RhoGAM was available,  Rh negative mothers gave birth to Rh positive  babies  and  everyone  usually  fared  well.    The  most  common effect  was that each subsequent baby was a little bit “yellower".    When a sensitization occurred in a mother,  (which was rare),  her future Rh (+) babies suffered.    Though rare,  it was severe for the baby. The advent of RhoGAM has reduced the effects for those babies considerably.

The use of Rh(D) immune globulin (trade name:  RhoGAM)   has been of great benefit in  preventing  sensitization of an  Rh (-) mother by an Rh (+) baby, thus preventing hemolytic disease of the newborn in a future pregnancy, administered within 72 hours after birth. It is derived from the plasma of a person with high levels of Rh antibodies. It is a solution of gamma globulin containing anti-Rh.    It  acts  to  prevent  and  suppress  the Rh immune response in the mother before she reacts to (or) builds antibodies  to  the  foreign  blood  group in her system.   In other words,  it removes the positive blood from her bloodstream by apheresis before antibodies form.

One reason RhoGAM has been questioned by parents is the preservative used in it, Thiomersal. Thiomersal, formerly and still commonly known in the United  States  as  thimerosal,   is  an organomercury compound  (approximately 49% mercury by weight). It was developed and registered under the trade name Merthiolate in 1929 by the pharmaceutical company Eli Lilly and   Company,   and  has  been  used  as  a  preservative  in  vaccines,    immune  globulin  preparations,    skin  test  antigens, antivenoms, ophthalmic and nasal products, and tattoo inks.

The compound  is being phased out from most childhood vaccinations.    Packaging the vaccines in single-dose vials eliminates the need for bacteriostatics such as thiomersal.

I am pleased Thimerosal  is no longer used in RhoGAM and that it is being discontinued from other vaccines as well.   Continue to ask your physicians if they have the Thimerosal-free products.

 Here are a few notable sites of reference on the use of Thimerosal in RhoGAM and other vaccines:

http://www.en.wikipedia.org/wiki/Thimerosal/
http://www.rxlist.com/cgi/generic/rhogam.htm

Reducing the Risk of Blood Mixing

There are ways to lessen the risk of blood mixing during and after birth.    However, blood  mixing can silently happen,   even with no visible  sign  of  a  bleed  that  would  indicate the possibility.    It sometimes happens  during  pregnancy with no sign, though it is less likely to silently mix during pregnancy  than  during  birth.  If a mother has suffered a physical trauma such as falling  or a car accident she should consider receiving RhoGAM prenatally,   even if she chose not to originally.    One of the most likely times a Mom is at risk of blood mixing is during a miscarriage,  and  is  a  very  important time to receive RhoGAM for all her future  Rh (+)  babies.    Bleeding  that  originates from the placenta anytime during pregnancy will likely result in blood mixing.   After birth,  delaying cord clamping until the placenta is delivered  and  allowing the placenta to detach on it's own with little or no traction of the cord lessens the risk of blood exchange between a baby and mother.

© 2007 Susan Oshel, CPM, used by permission.
(Charis newsletter readers are welcome to reprint this article as long as all copyright information remains intact. ~Editor)