Every sample from a patient is tested to determine whether there is sufficient feto-placental DNA to provide a reliable result. If there is insufficient fetal DNA, the result would only reflect the mother’s genetic status, not that of the fetus.
Our commitment to quality means that we will only provide a result when there is very clear evidence for, or against, the presence of a specific disorder. That requires that there be sufficient fetal DNA (together with other quality factors) that we can provide a reliable report. The reason why we cannot report a specific test usually reflects the complex biology of genetics and pregnancy rather than a technical failure in the laboratory.