The concern when the mother is Rh negative (and the father is Rh positive) is that Rh incompatibility may arise with each pregnancy. The problem does not affect the first pregnancy, but does each subsequent pregnancy.

This is how it works: during a delivery (or miscarriage or abortion), Rh factor from the fetus (which it inherited from his or her father) enters the mother's circulation. The mother's body, seeing this as something foreign, develops antibodies against it.

The antibodies themselves are harmless – until she becomes pregnant again with another Rh positive baby. Then the antibodies cross the placenta and attack the fetal red blood cells, causing anemia, which may be fatal.

Today, prevention of the development of Rh antibodies is the key to protecting the fetus when there is Rh incompatibility. Giving mothers a dose of Rh-immune globulin (Rhogam) at 28 weeks and after delivery can prevent serious complications.

Your initial miscarriage is considered your first pregnancy. At this early a gestation, (three to four weeks), the risk that Rh factors have entered your circulation is quite low, and your second miscarriage is probably not due to Rh incompatibility.

There is a test available that will check if you have developed antibodies to the Rh factor. Discuss this with your health care provider.

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