We're at the halfway point. Or maybe just a little past it, if you decide to come early like your siblings did. Looking at the pictures I've taken so far, I don't appear to have changed in size very much, which seems strange to me, initially. Then, I have to remind myself that with my first baby (your sister) I was hardly showing at all until I passed 18 weeks to begin with. And that's how it's supposed to work, after all. The really obvious growth will start to happen in the next few weeks. As far as you've come in the last twenty, you're still a tiny thing, and less than a pound in weight.
Not for very long, though. You've only got about 4 ounces to go to hit that measurement by now, and you'll do so fairly quickly, I'm sure. And much as the pictures fail to capture it, I can see the changes occurring from my own personal perspective, up above you. I think you've just gone through some sort of growth spurt, because I could swear that my belly experienced a visually perceptible expansion outwards between yesterday morning and yesterday evening.
Maybe by next week, everyone else will be able to see it, too. Or maybe not until the week after. (Or the week after that.) But that's okay, because I know you're doing hard work in there, growing and kicking and dancing. And that's all that matters to me.