There are four blood type categories: A, B, AB and O. Blood type is determined by the types of antigens (proteins) on blood cells. The plus or minus sign after the blood type is the Rh factor, a type of protein on the surface of red blood cells. Eighty five percent of the population is born with Rh positive (Rh factor) blood, according to the American Pregnancy Association. The other 15% are born Rh negative (lacking the Rh factor) and if a woman is Rh negative and gets pregnant, she needs to take some precautions.
Rh Negative and Pregnant
A simple blood test can confirm whether a woman has the Rh factor. If a woman is Rh negative and pregnant, what can happen is the woman's body can develop antibodies to an Rh positive fetus. If the woman's blood and baby's blood mixes, the woman's body may react as if it is allergic to the fetus.
The woman's and baby's blood is separated by a thin membrane but may mix after trauma, a miscarriage, an ectopic pregnancy, induced abortion or menstrual extraction, chorionic villus sampling or a blood transfusion.
The woman's body will become sensitized and the antibodies will cross the placenta and attack the fetus's blood by breaking down his/her red blood cells and produce anemia. This can cause severe illness, brain damage or death in the fetus or newborn.
Sensitization
A mother who is Rh sensitized will be checked during her pregnancy to see if the fetus is developing the condition. Treatment will not help once the woman develops antibodies. Once the baby is delivered on time, s/he may need a blood transfusion to replace the diseased blood cells with healthy blood.
In more severe cases, the baby will have to be delivered early or given transfusions while still in the womb.
Prevention
The best way to prevent antibodies from developing is by following the doctor's advice and having these tests and shots given:
- A blood test to determine blood type and Rh factor
- Another blood test called an antibody screen to show if an Rh negative woman has developed antibodies to Rh positive blood
- A shot of Rh immunoglobulin (RHIg) that can prevent sensitization of an Rh negative mother
Rh immunoglobulin (RHIg) Shot
An RHIg injection will be given to a pregnant Rh negative woman during pregnancy and after delivery. The woman will receive the first shot around week 28 of her pregnancy as well after delivery, especially if the woman delivered an Rh positive baby because blood can mix during labor.
A woman should also receive the shot after a miscarriage, ectopic pregnancy or induced abortion to prevent any chance of antibodies attacking a future Rh positive fetus.
The shot is only effective for the current pregnancy so with every subsequent pregnancy, she will need to repeat doses of RHIg.
RHIg may also need to be given after amniocentesis since blood could mix during the procedure.
If a woman decides to have her fallopian tubes tied and have no more pregnancies, RHIg should still be given. This is because the woman may decide later to have the surgery reversed, there is a small chance she can still become pregnant after sterilization and it will prevent her from developing antibodies if there is a need for a blood transfusion later in life.
Pregnant women should talk to their doctors about their blood type to make sure they are getting the best care available to ensure their pregnancy is a success. Most Rh negative women have successful, healthy pregnancies because of the knowledge and technology available for treatment.
Source: American Pregnancy Association
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