I don't mean to be cruel but are you aware of how many different sets of hands you may have in that area during labour?
This.
Have you considered what you may beed if your labour and birth isn’t straightforward? Is a manual examination, forceps, ventouse, anyone touching you at all also going to be triggering?
As pp said you absolutely have the right to refuse any examination or intervention.
But what if the decision is either have the intervention or lose your baby?
If you feel so strongly about a TV scan, it may be worth considering a section, or at least discussing what you can and can’t accept with your team.
You can try for a vaginal birth, and switch to a section if intervention is necessary, but be aware sometimes you have no choice- if you are past a certain point a c-section may not be an option.
Also consider if you do have a section that doesn’t necessarily mean there’ll be no contact with your genital area. Pain relief is often given by suppository, people will check, apply pads for bleeding, you will be catheterised etc.
Please get some counselling or help so you know what to expect. It a TV scan is such an issue, it would be better to have expectation managed before any decisions have to be made during birt.