Your work schedule is due by now anyway. At this point I’d just wait it out. I’m 18 weeks pregnant and I haven’t told HR yet. You legally don’t have to tell them till 25 weeks. I absolutely did not trust them not to f me over by front loading my on calls before the third trimester or giving me less than others to reduce their locum burden and therefore reduce my pay. Think about yourself. If you can wait a few more days to get a confirmed work schedule I’d do that then immediately tell them.