When I went through it, I told my manager and he was very supportive. At the time my employer didn't have a specific policy for fertility treatments, but I got in touch with HR to know more. For me it was helpful that my manager knew and he didn't share it with anyone else. I think it depends on your work place.
I think it’s necessary to tell your manager as you will need quite a few appointments for fertility treatment. Your manager will surely keep it private? Most workplaces have a policy for fertility treatment and time off for that
I agree with everyone above. I too was like you and still am a private person and don’t like people knowing my business, so I initially didn’t tell my manager and used to use my annual leave to take time off for appointments. But I kept having failed rounds and it all got too much. I ended up then telling my line manager who was very supportive and even told me they class ivf appointments the same as they would maternity so it would be paid leave, so I was actually using my annual leave unnecessarily all that time. They have to keep it confidential anyway so I would think about telling them as you never know how your treatments will go. I ended up going off sick after I had a few failed rounds and a loss, and they were more supportive as they knew what had been happening.
Do you have a good HR team?