They run very, very small.

I just wanted to warn you new mom's or soon to be mom's. I have my 3 1/2 month old in a 18 month Gerber onesie right now. I have so many Gerber onesie's that she didn't even get to wear because they're just too darn small! She wears 6 month for everything else. So when your sorting your clothes, make sure you check the brand and get those Gerber clothes to the front!