Isla is also in size 1's & 12 months & they still fit her well. A bit narrow maybe but no leaks yet. I don't even use a snappie anymore I just put a good cover over the top & it stays on well. I will probably look at getting more for a newborn.
Sorry I was refering to the size clothes Isla wears. Pretty sure mandy macs are just the one size being OSFM