Answer:
The cells analyzed might be a mosaic of different genomes
Step-by-step explanation:
The human genome in every cell might not be the same and could give us some misrepresentation of what really happens on our genome. Chromosomal abnormalities are also a very common phenomena to be observed in human cells. For those differences in the genome of the child the test might have identified some altered cells with a type of chromosomal abnormality which was not latter identified or the abnormal cell might be also eliminated by its abnormal nature.