Both my babies were born very close in size. I havent checked yet, but I think they were the exact same length even. Both breastfed exclusively, on demend. Both started out in 0000s.
I have no idea how long DD is now but she is now fitting into the smaller of the 00s! And Im not talking about the bonds 'one size smaller than every other brand' thing. I mean a normal 00. So I went through my photos of DS first 6 months and discovered the photo of him in the exact same onesie as DD is wearing tonight...

Top is DS @ 5 months
Bottom is DD @ 8 weeks

https://www.bellybelly.com.au/forums...40-8-weeks.jpg