Typically women get an ultrasound at the end of the first semester and another one around the end of the second trimester (this is the one where sex is usually determined, although wikipedia claims sex can be determined as early as 16 weeks). So that would mean she ought to get pregnant between November and January-ish.

There's something bugging me about time zones. In L.A the blackout flashed people to 10p.m. So what kind of clinic does routine ultrasounds at 10p.m? Or is Janis not in L.A anymore?

Also, for that matter, isn't it a bit strange for Stan to be reading his paper in the bathroom in the middle of the night? Or is he also somewhere else?