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Pregnancy can be the first time that some women learn their blood is Rh negative, which applies to about 15 percent of the population. A person who is Rh positive has an antigen or type of protein on the surface of their blood cells that can generate a response from the immune system. About 85 percent of the world’s population is Rh positive, meaning they have these antigens, while the other 15 percent is Rh negative because they don’t. Being Rh negative is not a health issue until the person needs a transfusion or becomes pregnant.
If a mother is Rh negative and her child is not, it’s important to prevent any possible health issues.
What is the Rh factor?
The Rh factor is so named because it was first identified by scientists in a rhesus monkey in 1937. It has since been discovered that each person inherits one blood type gene from each parent and one Rh factor, plus or minus. The only way for a person to be Rh negative is for both of their parents to have one negative factor and for them to inherit it from both parents.
Since most people are Rh positive, it’s likely that an Rh negative individual might have a child with an Rh positive one and this can pose a problem.
If a mother is Rh negative and her child is Rh positive, her child may be at risk for developing hemolytic anemia, which destroys healthy red blood cells. If the two incompatible blood types mix, the mother’s immune response can produce antibodies that travel through the placenta or pass into the baby’s blood at birth, because of trauma, or during a test such as amniocentesis. The antibodies damage the baby’s blood cells.
Problems don’t usually occur during the first pregnancy since the mother has not yet had time to become sensitized, but once that does happen it can affect subsequent pregnancies. It does not only happen after a full term pregnancy. An ectopic pregnancy, abortion or miscarriage can also cause a mother to become sensitized putting subsequent pregnancies in danger.
What can be done?
Fortunately, there are simple ways to prevent sensitization.
The first thing both parents should do when they find out they are expecting is to take a blood test and determine whether they are Rh negative or positive. Two Rh positive parents won’t have a problem, nor will two Rh negative parents but if the mother is Rh negative and the father is positive, it’s wise to take preventive measures. The baby’s blood may also be Rh positive.
The best way to protect your baby is get a shot of an Rh immunoglobulin (RhIg), known commercially as RhoGAM, which prevents your body from producing antibodies. It doesn’t work if the mother is already sensitized and producing antibodies.
The shot is usually given at about 28 weeks of pregnancy, within three days of the birth of an Rh positive infant, or in any situation where your blood may potentially mix. Your healthcare provider will also closely monitor your baby’s health for signs of blood cell damage and possibly use amniocentesis or an ultrasound test to screen your baby’s heartbeat and blood flow.
You can take a blood test, called an antibody screen, to show if you have developed antibodies. If babies do develop Rh disease, a blood transfusion can restore red blood cells, with transfusions possible as early as 18 weeks.
Prevention is the best treatment
The best treatment for Rh disease is prevention. Having a preventive shot is much easier than dealing with any potential complications. Always let your healthcare professional know about any previous pregnancies and any bleeding that may have occurred.