Telling your employer you are pregnant
You need to tell your employer you are pregnant by the 15th week before your due date. You will also need to inform them when you wish to start your maternity leave (giving them at least 28 days notice).
How early you share the news of your pregnancy is again a personal choice. Obviously, the earlier you tell your employer, then the sooner they will be able to adapt your job to make it safer for you and your baby. If you do a job that could be harmful to your pregnancy then you would really need to inform your employer straightaway.
If you want to take time off for antenatal appointments, maybe you could tell your boss of your pregnancy in confidence and share the news with your colleagues when you feel ready.