I'm planning on getting pregnant soon. However, my husband and I are the same blood type: A positive. Someone told me that our having the same type of blood will cause the baby to be defective. Is this true? If so, is there treatment for it?

A.C.

There is absolutely no risk to sharing the same blood type. The pregnancy risk normally associated with blood type has to do not with the ABO factor (the letter designation in blood type) but with the Rh factor (the "positive" or "negative" designation). A woman who is Rh negative may develop antibodies to her baby's blood if the father -- and thus the baby -- is Rh positive. Untreated, these antibodies can attack the blood cells of the fetus. This is easily prevented with an injection of a substance called RhoGAM that blocks the formation of these antibodies in the mother. In rare cases, an intrauterine blood transfusion may be necessary. Blood testing and RhoGAM shots (when necessary) are a standard part of prenatal care.

We often recommend pre-pregnancy screening for Rh and other, rarer abnormal blood antibodies that may affect a pregnancy. Testing the man is necessary only if the woman's test reveals abnormal antibodies. Luckily, the presence of antibodies that can cross the placenta and attack the baby are quite rare. If you do have such antibodies, or if you have had a prior pregnancy in which hemolytic disease (in which antibodies attack the fetus) occurred, then you and your husband may want to consider using donor sperm to avoid this risk to the fetus.