If I know I'm pregnant now (1month), how long do I need to inform the company? What if they terminate me? :(

Other mummies have mentioned. They can't terminate you. For me and my friends, usually our direct superior will be the ones to know before our other friends. The reason is because we tend to feel unwell during our first trimester be it dizzy spells, fatigue or inability to focus. That is the most important period to request for their support and understanding. I guess most employers and superiors are acceptable of pregnancies in the company and I also think that they appreciate you giving ample notice so that they can make arrangements for someone to cover your duties.