When you're going through treatments/interventions to aid in your journey to pregnancy, are there any appts that can be a "on the fly" or "come in when we call you" type situations re: IVF, IUI, etc.?

DH has an employee going through some infertility treatments, and while he wants to be sensitive/cognizant of all the medical procedures/sick time he will need; he is trying to stay ahead as far as not scheduling her, etc. around her medical appts; but she's had quite a few that have been last minute, a couple hours before, etc.

I have no idea how appts are in this area and was wondering if you could provide some educated feedback that I can tell DH.