Rh Factor

The RH factor is a substance found on the red blood cells of most folks. Eighty-five percent of people have this and are said to be Rh positive (Rh+). Fifteen percent don’t and are Rh negative (Rh-).

There is no importance in most situations except if, by chance, the blood of an rh+ person gets into the blood of an Rh- person. The Rh- person would develop antibodies in his blood to fight off the strange “invader”. This would never happen except in a mismatched transfusion of in the case of an Rh- woman pregnant by an Rh+ man. Her unborn baby would often be Rh+ and under certain conditions, mainly during childbirth, their blood could mix. (Usually, it doesn’t). This would cause the mother’s blood to get sensitized and form antibodies against the substance in the baby’s blood. These antibodies destroy the baby’s red blood cells. This usually won’t harm a first baby because he would already be out by the time the antibodies were formed and they wouldn’t get back into the baby’s system. But the antibody response is stored in the body and the antibodies can pass from the mother’s blood to the baby’s blood through the placenta, and so could harm the blood of her next baby.

Fortunately, there is a way to control this. An Rh- mother with an Rh+ husband should have her blood checked for antibodies several times during pregnancy. Most likely, they will not show antibodies. Then, the day after birth, the Rh- mother will need a shot of Rhogam to prevent any antibodies from forming in case the blood did mix. Consult with your doctor on how to go about getting the Rhogam shot. This shot must be given with 72 hours after birth in order to be effective. If the Rh- mother’s baby is Rh- she won’t need the shot because their blood would not be antagonistic.

If she has had several children, miscarriages, or abortions and has a high antibody count or for some other reason her antibodies are high, she will need to deliver in a hospital where they can induce labor early to get the baby out of a hostile environment, and transfuse if necessary.

There is no complication from an Rh+ mother and an Rh- father. If the baby was Rh- like his dad, his blood would not have any extra substance in it to mobilize his mother’s defenses.


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