Rhesus disease

Rhesus Hemolytic Disease

Rhesus (Rh) factor is a group of proteins that occurs on the surface of some people’s red blood cells. If you have Rh factor on your red blood cells, you are referred to as Rh-positive. If you do not have Rh factor, you are Rh-negative. Rh incompatibility is when an Rh-negative mother becomes pregnant with an Rh-positive baby. If the unborn baby’s Rh-positive red blood cells cross the placenta and reach the mother, her immune system will produce antibodies that will destroy the baby’s red blood cells. This is the cause of a complication called Rh hemolytic disease in the unborn baby.

A baby with Rh hemolytic disease may be born with jaundice or anemia. The most severe symptom, which can be diagnosed by ultrasound during pregnancy, is the accumulation of fluid, called hydrops, in the baby’s body.

Preventing Rh incompatibility

Early in pregnancy, blood tests are done to determine the woman’s blood type and Rh factor. Women who are found to be Rh-negative are given an injection of Rh immunoglobulin, also called Rhogam, during and after pregnancy. This is an antibody that blocks the woman’s immune system from producing the antibodies that destroy the unborn baby’s red blood cells. Women who are Rh-negative should be given the injection in all their pregnancies. Rh immunoglobulin is given at 28 weeks of pregnancy, and again within 72 hours of childbirth. The injection is given after an amniocentesis, after any episodes of vaginal bleeding, and at any time where the placenta could be disturbed, such as after a blow to the stomach. Rh immunoglobulin is also given to Rh-negative women after any miscarriage.

What to expect throughout pregnancy

If the pregnant mother is Rh-negative, the mother’s blood will be tested for antibodies throughout the pregnancy. If there are Rh antibodies in the mother’s blood, the father of the baby should also be tested for Rh factor. If he is Rh-negative, the baby will be Rh-negative, and therefore is not at risk for Rh hemolytic disease. If the father is Rh-positive, the pregnant mother will be offered an amniocentesis to determine whether the unborn baby is Rh-negative or Rh-positive. If the baby is Rh-positive, the baby’s health will be monitored using ultrasound, and amniocentesis or another test called cordocentesis may be done throughout the pregnancy to determine if the unborn baby is developing Rh hemolytic disease. The tests need to be done every two to four weeks, and pose a small risk of miscarriage.

If the unborn baby shows signs of Rh hemolytic disease, early labour may need to be induced, so that the mother’s antibodies do not destroy too many of the baby’s red blood cells. If Rh hemolytic disease is severe and labour cannot be induced yet, it is possible to give the baby blood transfusions while still in the womb. Through proper treatment, it is possible to save the lives of over 90% of babies who have Rh hemolytic disease.

References

Special Pregnancy Program

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Fetal Medicine: 416-586-4800 x 7756
Fax: 416-586-3216

Maternal Medicine: 416-586-4800 x 7000
Fax: 416-586-5109

Main clinic hours: Monday to Friday, 8am to 4pm

Prenatal Diagnosis & Medical Genetics

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phone: 416-586-4800 x 4523
fax numbers:
416-586-4723 or 416-586-8384

Perinatal Mental Health

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Phone: 416-586-4800 x 8325
Fax: 416-586-8596