The same way the state does.

Flip it around. If a woman consents to have sex with a man but then gets pregnant even though he wore a condom that is not rape. That is birth control failure. It haopens. None of them are foolproof. She still consented to the sexual act.

If she’s not on birth control, has no alternate methods of her own on hand and agrees to sex but wants to wait to get squared away and THEN he lies, claiming to have had a vasectomy just so he can have sex, that is rape. His lie has deprived her of meaningful informed consent.

The same metrics apply.

If you have consensual sex with a woman without wearing a condom and she’s on birth control pills or has an IUD and she gets pregnant, you have not been raped. You have birth control failure. You did not choose to act to prevent it regardless of her actions to do so.

If you agree to have consensual sex with a woman, go to pull out a condom, and she quickly pulls out a different one of hers and convinced you that it’s better for whatever reason and you agree to use it instead but she lied and created a condom failure (poked holes in it), then you might have a case for 3rd degree or coercive rape. You still have to prove that you would not otherwise have had sex with her without the lie in place making you think you were safe.

But good luck proving it. If you go forward, you’ll have your entire sexual life combed through. Every inch of it scrutinized. Hope you weren’t drinking, because if you were you were probably just asking for it. You know how it goes.

What is it? Something like out of every 1000 reported rapes, 7 lead to conviction and 6 end in incarceration? Might as well not bother with legalities.