As the only person in the company, what should I tell the leader if I am pregnant?

First of all, arrange your vacation time and work content according to your pregnancy and physical condition.

Then, communicate directly with the personnel or direct leadership.

You can say, "I'm pregnant, but you don't have to worry." I plan to take maternity leave in X. Before that, I will finish my work or arrange handover. There are a few specific things. . . . . . I'm going to finish it in xx, and then I'm going to give it to xx. If everything is normal after delivery, I plan to come back and work in X "and so on.

Any normal leader will not take you for granted. Male leaders also have wives/girlfriends/children. No one can understand this, especially if the work arrangement is clear. Don't underestimate leadership.