Actually, there are safer positions! Firstly, condoms, they are about 97% effective. Why not 100%? Cos they can break, there may a faulty one, they may come off etc.
Secondly, STI's. Yes of course sex involves putting your nobend in a pussy, no change there, but, some STIs can be transmitted even with a condom on, herpes, warts, crabs for example.
If you have sex in missionary, or you standing up with her legs over your shoulders, you can ensure you fuck her but with only the condom protected part of your cock going inside. Ensure its rolled all the way down. Naturally, if she is dripping wet, you wont help get some juice around the base of the condom. but this position can help minimise contact with her skin against your skin which isnt covered with the rubber.
Probably the most risky positon is her on top. Its deep and her pussy lips will be touching your base of your penis, and her juices will flow downwards, down your bollocks. Plus, if the rubber snaps, it may not be as noticeable.
So, actually, its a valid question!
Mind you, if you are THAT paranoid about catching an STI and what position to have sex, maybe its time to take up chess?