this will be encouraged through gaslighting and lies by the cheat, who will only admit to what is known (e.g. you might have had a relationship with him for quite a long time, but she will be told you were a drunken one night stand or whatever plausible excuse minimises your relationship).
"She's crazy, obsessed with me, delusional, mentally ill, lying"
She's produced proof you shagged her.
"It was only once, I was drunk, down",
She's produced proof you shagged her more than once.
"I'm depressed, suffering from sex addiction, you've been ignoring me, we haven't been close" ....
She's pregnant
"it's not mine"
"it was a one night stand"
"the condom must have broken",
"she must have tampered with the condom"
(he wasn't using one, and pregnancies from one one off incident are not that common, most couples have to fuck repeatedly to hit that 10-15% chance per cycle in your eg 30s)
On and on.
There'll be sex addiction talk and depression talk and stress talk and childhood trauma talk and subtle or not so subtle blame put on the wife ("cheating doesn't happen in a vacuum") and counselling will be broached as the solution etc etc etc
Cheating actually does happen in a vacuum. The vacuum is the cheater's morality/integrity.