Rh Factor and Pregnancy

The Rh factor refers to the type of protein on red blood cells. Most people have the Rh factor and are thus labeled Rh positive. Others do not have the Rh factor and they are Rh negative. If your are Rh negative and you become pregnant by a man who is Rh positive, there is the potential for problems.

Sometime before you deliver you will have a blood test to find out your blood type. There are four blood types - A, B, AB, and O.  Each of the four blood types is additionally classified according to the presence of a protein on the surface of red blood cells that indicates the Rh factor. If you carry this protein, you are Rh positive. If you do not carry the protein, you are Rh negative.  The Rh positive factor is much more prevalent than the Rh negative factor with only approximately 15% of people in the world being Rh negative.

The Rh factor can cause problems if you are Rh negative and the man who impregnates you is Rh positive. The baby growing inside you, the Rh-negative mother, may have Rh-positive blood inherited from the father. If your Rh-negative blood comes in contact with the baby's Rh-positive blood, serious problems can arise.  If during delivery, a transfusion, miscarriage or ectopic pregnancy, your blood and your baby's blood intermingle, your body may begin producing antibodies to fight what it perceives as this foreign Rh positive substance.   While Rh incompatibility rarely causes complications in a first pregnancy, during a subsequent pregnancy the Rh factor can result in severe anemia, jaundice, brain damage, and heart failure in a newborn.

To protect against Rh factor problems, you should have a blood test done at an early stage of pregnancy.  If you are Rh negative, your health care provider will give you Rh immune-globulin shots around the 28th week of pregnancy to prevent sensitization for the rest of the pregnancy. Shortly after birth you may again be given Rh immune-globulin shots.  This treatment will help prevent you from making antibodies to the Rh-positive cells that may have entered your bloodstream.

Accordingly, it is important to start regular prenatal care as soon as possible and to discuss the Rh factor and any other concerns you may have regarding your pregnancy with your health care provider.