By when is it required to tell employer that we are pregnant?

On MOM website, you are required to inform your employer at least 1 week in advance (before delivery) to be eligible for the full benefits of maternity leave. Of course it is advisable to let them know as early as possible - so they can plan for people to take over your work while you are on leave. Most people inform their bosses after about 3 months (because pantang hahaha) Do whatever you think is most comfortable for you :)