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Rh Incompatibility

Description

In more than 98% of cases, red blood cell incompatibility between a mother and the baby she is carrying involves the Rhesus or Rh D antigen so the disease is known as Rhesus disease , Rh disease or Rh Incompatibility .
If a Rh-negative woman conceives a child with a Rh-positive partner, the potential exists for the child to inherit its father's Rh-positive blood type.

During the birthing process , blood cells from the unborn child can escape into the mother's bloodstream. These cells are recognised as foreign if they are Rh-incompatible (Rh positive compared to mother's Rh-negative) and a natural rejection process will ensue with the formation of antibodies. The process is known as red cell alloimmunisation and typically occurs after the delivery of a baby at the end of pregnancy, but other pregnancy-related events such as ectopic pregnancy , chorionic villus sampling , amniocentesis , elective abortion or spontaneous miscarriage can result in antibody formation. Although the pregnancy in which the alloimmunisation first occurs results in an unaffected child, future children are at substantial risk, as in subsequent pregnancies, newly formed antibodies in the pregnant woman can cross to her unborn child and attach to its red blood cells producing anaemia and in the worst case scenario, foetal death.
Data from the U.S. Centres for Disease Control indicate that the incidence of haemolytic disease of the newborn secondary to Rhesus disease is approximately 1 per 1000 live born infants.

Prevention & Treatment

Medication is available to prevent Rhesus disease. Rh0(D) immune globulin should be administered to the Rh-negative woman with a Rh-positive partner any time there is a chance foetal cells may enter the pregnant woman's circulation. Rhesus immune globulin should be administered routinely at 28 weeks of pregnancy and after the delivery of an Rh-positive infant. If given correctly, this medication is more than 99% effective in the prevention of Rhesus disease. Rhesus immune globulin is only effective in preventing Rhesus disease; it is not effective in preventing worsening disease once alloimmunisation has occurred.

In 12% of first affected pregnancies, the infant may require intrauterine transfusions. In this procedure, a needle is directed under ultrasound guidance into the umbilical cord and blood is infused directly into the foetus to correct its anaemia. The procedure is usually repeated at 2 to 3 week intervals for the remainder of the pregnancy until approximately 35 weeks of the pregnancy. The survival rate after intrauterine transfusion is approximately 85%.

The information in this page is presented in summarised form and has been taken from the following source(s):
1. The University of North Carolina, Department of Obstetrics & Gynecology, Women's Wellness & Specialty Services: http://www.med.unc.edu/obgyn/


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Rh incompatibility
 

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  http://www.hon.ch/Dossier/MotherChild/complications/complicate_rh.html Last modified: Jun 25 2002