Why is it what when you get pregnant your nipples and areolas get dark af and expand to another dimension? Im not pregnant yet but I've read here from many women this happens and my areolas are already medium size and I have small boobs (B cup) and they are perky which I love.

I would hate for the areolas to expand and get dark even more. I'm latina and my areolas are a light cinnamon color. My skin color is like a beige/soft tan. Do they get back to normal after giving birth??? Do they sag? Stretch marks? I know this all sounds very vain but I must know what I'm getting myself into. My image is important to me as well as having a baby.