That event, Cold Air of an Encroaching Winter, takes place during the second reset, towards the end of Chapter One of the game. After the first Halloween, before There Is Nothing. The "Ayane was pregnant" theory is about the third reset, since that's the one where she starts acting weird and all the clues are dropped, and includes the fact that at the start of it, right after There Is Nothing and the transition to winter, there is an event where Ayane sneaks into Sensei's room, they have sex, and he finishes inside her (thus guaranteeing that literally everyone who plays LiL will have unprotected sex with Ayane, regardless of what choices they make in repeatable scenes or lust scenes they do). So that means the conversation you're depicting takes place from before Ayane got pregnant.
But seriously, as akselx says:
But I guess some people won't be convinced unless someone literally tells Sensei flat-out that he got Ayane pregnant -- which I guess would have to be Maya, since nobody else knows due to the resets and Sensei is in heavy heavy denial. But hey, we've got Maya events coming tomorrow. It could happen.Yeah, I don't believe Sel would have bothered inserting poem about a loss of child and having Sensei semi-consciously pulling out of Ami in the sex scenes that followed.