Excuse for egg retrieval

I have a new boss at work and don’t feel safe yet to tell them I’ve been doing <a href="https://glowing.com/glow-fertility-program">IVF</a>. I haven’t had to take off work for the early morning appts, but I got two days notice I have to take off for egg retrieval. I told my boss I have to have a medical procedure done, but I want to have an excuse for if he asks what happened so suddenly. Any suggestions on what I could say I had to do? Thanks!