Just wondering if I need to tell Centrelink I am pregnant? Or just file the papers when bub is born?

I am divorced with two kids, and have been with my current partner for 3 years. We have never moved in together though, as the baby was a surprise and he lives at home with his elderly Dad (who is very ill with heart condition at the moment). We will live together eventually. But right now this is the status quo.

Any advice?

Cathy