A check on chromosomes would not necessarily give a prediction about whether or not the child would at a later date wish to change gender.
Not every child who wishes to change gender has the chromosomes of the gender they wish to embrace.
For example, not every girl who wishes to transition to the male gender has an "unidentified" Y chromosome.
Many females wishing to transition to males would have the usual XX chromosome pattern seen in females, yet they still yearn to live their lives as female.