Hello and welcome to health care magic,
there will always be alteration in the blood flow to different organs and in this case you may get a condition called the vascular tinnitus
which may be what you are suffering from.
Unfortunately no scan can be done in your condition as this may harm the baby
The same reason is why even medication can also not be given to you
In any case if the sound is not very high then you can just ignore the same and in all probability the sound will go away when you deliver.
If however it persists beyond that then you must get an audio testing done along with MRI
of the temporal bone
and get back to me or any ENT with the reports
Meanwhile do not worry and take steam inhalation and just ignore the sound
Dr Sriram Nathan