Here's an idea. Probably not the case, but it does fit with Ralph's inability to think ahead and his impulsive behaviour:
He sent that message to Mr Vickers claiming Faith is pregnant (mid argument for context) not because she actually was, but just to piss of Mr Vickers. Of course Mr Vickers then leaked it and people assumed it to be true. Ralph could not deny it without looking scummy and stupid, so he figured he'd just ignore it and hope people forgot about it. Then Dark Butters called into the show and mentioned it, wanting to congratulate Ralph for those sweet goldstar caller brownie points. Of course Ralph actually got annoyed and booted him instead because now everyone in his audience knew what he had claimed. Since then Ralph has had no choice but to pretend it's real just to save face. He's too deep in the lie now, his only options are to either get her knocked up for real and have a kid, or fake a miscarriage/abortion, opening himself up to stillbirth/abortion jokes given his past with Sargon and CRP.
Personally I think Faith actually is pregnant with the demon baby and we all witnessed its conception during the poo tape, but I do love the idea of Ralph inventing such an absurd lie and going this far with it just out of petty stupidity.