You dont have to tell as it is against the law for them not to hire you on that basis!
So i wouldnt tell. After a few weeks (or months) when you are ready to tell them then try. They cant fire you, stop you from attending training or diadvantage you in anyway for the pregnancy and if they do then they are up for alot of trouble in the antidiscrimnation laws.

In my personal experience, i was 10 weeks pregnant at my job interview but i knew that my pregnancy would not effect my chances of the job (casual position) and also it was important for them to know for work related risks.

since working - my coworkers are aware of my pregnancy and they are really good with helping me out and giving me suitable clients to my condition (lol condition). I still can attend training and no have not been discriminated against.

i hope the interview goes well.