The anti-M blood antigen antibody is an unpredictable antibody that is an uncommon cause of hemolytic disease in newborns, according to the National Institutes of Health. Though studies show that the anti-M antibody has been found in a high number of pregnant women, the chance of a newborn developing hemolytic disease is very rare.
In a study conducted at Ohio State University from 1969 to 1995, 90 women who had 115 pregnancies were found to have the anti-M antibody, states the NIH. If there is no history of pregnancy complications, the presence of the anti-M antibody should be of little concern, and no further testing is recommended by the NIH. However, if there is a history of complications, more testing should be done later in the pregnancy to check for the potential development of hemolytic disease.
A 1989 study reported on the NIH website determined that there are three types of cases that represent the spectrum of findings when the anti-M antibody is present in the mother during pregnancy. In the first, the father's genetic makeup indicated that hemolytic disease would not occur. In the second, the infant did not develop hemolytic disease, despite the presence of the anti-M antibody. In the third, hemolytic disease was present and a blood transfusion was needed for the newborn.