Any hairstylists expecting?

Brittany • May 16th with first boy
I'm self-employed, FTM 20weeks 2days, and I'm having the hardest time with this scheduling time off thing. I book out pretty far so it's hard! My clients keep saying "I want to get into you right before you leave for maternity leave," but how am I supposed to know when to stop scheduling?! My due date is May 16th. I have known several stylists who ended up being on bed rest a month or so before their due date because of the job. But it's hard to know when I should technically stop scheduling out my appointments because I don't want to just stop working at the beginning of May and go without pay for a whole month if I'm feeling fine and he ends up coming a little later, but I also don't want to schedule people out and then have to cancel everyone and not be able to get them in before I leave. Any advice?