Ok either baby's clothing sizes are totally bogus or ava is growing faster than I thought. She not…

Ok either baby's clothing sizes are totally bogus or ava is growing faster than I thought. She not quite 6 months yet. These cloths are labeled for 12mo. They're also the same size or EVER SO SLIGHTLY bigger than her 6-9mo sizes. I like onsies the cover up her diaper in case I don't want to put pants on her, most of her 6-9mo sizes don't cover her up, this size onsie covers her up perfectly! Is there such things as perfectly sized baby clothes??