If you are in the UK, the sooner you say the sooner your employee can do a risk assessment which could mean modified duties.
I told my manager once I’d had my 8 week reassurance scan. I’m a community midwife and I was so unwell I needed a change of duties at work as the anti sickness I was taking made me too drowsy to drive and being in the car made me even more sick so being out on visits was just a no go for weeks My first pregnancy I was 5 weeks when I told work. We found out we were pregnant 3 days before we went into lockdown for Covid so I had to go non clinical. My manager knew before our families! Also in the U.K. if you tell them you are pregnant they have to then pay you for any antenatal appointments and any pregnancy related sickness can’t be used in sickness reviews
I told an employee at 10 weeks then had a miscarriage. A few years later I told a different employer at 9 weeks and had a miscarriage. This pregnancy I waited till I couldn’t hide my bump anymore at 19 weeks 🤣 just to be sure it would stick I was supported through every scenario but waiting felt better for me. Do what feels right!
I told at 6 weeks in case of a miscarriage and they knew then why I’d be off of work..
I was still in the military with my first when I was pregnant and gave birth. I got out while I was pregnant with my second. I told them right away so that I could get my pregnancy waiver which including not doing physical training, no arming/weapons stuff/ and no cbrn also couldn’t be sent on a deployment
When you want to. None of those activities technically disqualifies you from doing that job while pregnant unless your doctor says otherwise. I would say tell them around 2nd trimester stage. Some of those activities become more difficult as the baby grows.