I agree with pp on not telling just yet. I start work at 8/8.30am and was never late for work due to bloods / ultrasounds. I took 2 days off for EPU claiming "gastro" and then had ET at 7am and went straight into one of the biggest most important meetings of my career!! (That was the very first day I spent with my DS on board!!!)
Try it for a cycle or two and then tell work if you feel you need to.