When you visit your doctor or midwife for your first prenatal visit, blood will be drawn. The blood is checked for a variety of things and you may not give it much thought. One thing that is tested in this early blood work is the blood type of the mother.
One thing that is checked is the Rh factor of the mother’s blood. Human blood is either Rh positive or negative. For example, if the blood type is O, it can be either O positive or O negative. Prior to pregnancy, you may not have known what this means or may have never given it any thought at all.
Basically the positive and negative describes whether or not Rh factor is present in the blood. If the factor is present, the blood type is positive. If the factor is not present in the blood, the type is negative. Other than receiving a blood transfusion, pregnancy is the only time this can be an issue.
Since the majority of the population is Rh positive, this isn’t an issue for most women. The only time it is an issue is when the mother is Rh negative and the father is Rh positive. In this case, it’s possible for the mother and the baby to have opposite blood types. The mother is negative, but her baby could be positive, due to the father’s positive blood type.
In this case, the mother’s body will naturally begin to make antibodies against this Rh factor in her baby’s blood. In effect, her immune system will view the Rh positive baby as an intruder and possible threat to the mother.
This is generally not a problem in the first pregnancy, but can become an issue in subsequent pregnancies, since the antibodies to the Rh factor will be present in the mother’s body prior to the second pregnancy. At this point, the antibodies can actually attack the baby and break down the baby’s red blood cells. This can cause severe anemia and even death in the baby.
Fortunately, modern medicine offers a treatment for this problem. An injection called Rhogam. In most cases, the injection is given while the mother is still in the hospital after the birth of the first baby.
In some cases, the injection will be given in the beginning of the third trimester, before the baby is born. This is generally only done if the mother has had a previous miscarriage or abortion. In this case, the mother can become sensitized sooner putting the baby in jeopardy as the pregnancy progresses.
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