Sometimes pregnancy in dreams represents a new idea, project, or relationship. Perhaps there is something new in your sister's or a friend's life that you wish you could have---not necessarily a baby, but just something new.

I see a contrast between the tortoise and the rabbits. It's like that fable "The Tortoise and the Hare." I guess the best thing to do is describe the characteristics of a tortoise, then do the same with rabbits. See if you can find characteristics in both that you wished you possessed.