I might be mistaken, but I'm pretty sure there are more reasons besides abortion to perform this invasive kind of ultrasound.
There are plenty. However, the point is that prescribing that kind of diagnostic procedure is entirely dependent on what the doctor believes to be in the best interest of the patient in his care. You will notice a lack of gynecologists amongst the groups advocating for these procedures to be put into law.
You should never legislate medicine like this. This would really be no different from say requiring doctors perform a uterus lining biopsy before administering treatment to women. Both are medical diagnostic procedures, but each have their place and time in medicine and doctors are the best people to decide when that time and place is, not legislators.