In prenatal care, maternal blood screening for extra chromosomes in the fetus is becoming increasingly common. Such tests might give false-positive results if the mother's genome contains more than the usual number of certain DNA segments, especially if the fetus has inherited an elongated chromosome. The tests could be improved to account for the fact that chromosomes can vary in size and composition among people.

Source: Some false postive prenatal genetic screens due to mother's extra DNA segments


David Cottle

UBB Owner & Administrator