The knowledge, and sensation of being bare, naked, your cock skin-on-skin in married pussy, pumping cum into another man's wife is intensely powerful. Like a ....... I've impregnated my long-term lover Marie twice, over the span of two different husbands. I had a similarly intense experience with Ali, although it wasn't deliberate at first - initially she lied to me about her birth control, "tricking me" into impregnating her.
Ali confessed, before she tested pregnant, but that just made me want to fuck her more intensely.