My job required certain more risky elements, and also long hours, so I had to tell my bosses in the first trimester. Honestly, I think for certain kinds of work, it’s good to tell early so that they’ll be more careful with your work arrangements
Depends on your job nature. If there is risk involves, you may want to tell them earlier so that arrangement can be made. If is not and you want to tell them after first trimester, then meanwhile you may hint them.