How Blood Type Rh Factors May Impact Pregnancy

During your pregnancy, you will be required to have your blood type sampled as part of your pregnancy’s standard blood work. Testing your blood type not only identifies if your blood is type A, AB, B or O, it also identifies if the protein on your blood cells, known as the Rhesus factor or Rh factor is (+) positive or (-) negative. As a fetus, we all inherit our Rh factor from either our mother or father. If your baby’s father is Rh (+) and you are Rh (-) there is potential for your baby to inherit an Rh factor that is incompatible with your blood. This is important because there are certain health risks associated with an Rh (-) mother and an Rh (+) fetus.

The Rh factor has implications during pregnancy, only if the mother has an Rh factor that is negative and her fetus has an Rh factor that is positive. This is known as Rh incompatibility. Usually the blood of the mother and baby do not mix during pregnancy, however, if they do, serious health issues may arise. If the fetus’ Rh positive blood mixes with the mother’s Rh negative blood, her immune system will identify the fetus’ blood as “foreign,” which will in turn induce her body to produce anti-Rh antibodies. These antibodies have the ability to cross the placenta, which is a particular concern for the next pregnancy a mother might have. If the mother has another Rh positive baby, these antibodies will cross the placenta, and enter and destroy the fetus’ blood, causing many serious health complications, such as severe anemia, and possibly even death in the baby.

As mentioned, during pregnancy, it is unlikely for your blood to mix with your baby’s blood. However it is possible in certain circumstances, including, an accident or incident that causes trauma to the abdomen during pregnancy, bleeding during pregnancy, miscarriage or abortion, ectopic pregnancy, molar pregnancy, amniocentesis, chorionic villus sample, fetal blood sampling, or rotation of the baby in a breech position.

If you are Rh negative, it is recommended to get blood tests during your first trimester and 28th week of pregnancy to screen for the anti-Rh positive antibodies. If the blood work determines that your body has not produced any anti-bodies yet, you will need to receive an Rh immune globulin injection, which inhibits production of these antibodies from occurring. You will also receive this injection following delivery, if your baby is Rh positive and you are Rh negative. You should also receive this injection following any circumstance in which your and your baby’s blood may have mixed.

If you are interested in learning more about Rh factors during your pregnancy, schedule an Obstetric consultation with one of our specialized Garden OB/GYN Clinicians. If you have vaginal bleeding or have experienced any circumstance that you suspect caused your blood to mix with your baby’s, contact your OB/GYN immediately.


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