I wish someone had warned me about this minor detail before I purchased footed pyjamas for my little one. They grow up so fast, so it is always wise (when purchasing baby clothes in general) to get one size bigger than what would actually fit him/her. Not too big, just one size bigger, so that you can use it for relatively longer than you would have if you bought the exact fit. Also see how the metal snap-close buttons on the left baby pyjama are placed closer together (in comparison to the snaps on the right pyjama) – well I suggest always buying ones similar to the one on the left.
As the baby grows the wider gaps tend to open up exposing baby skin leaving chest and tummy bare when he/she wriggles around in her sleep at night, but if the snap buttons are found closer to each other, then the sleep suit actually buttons up well, keeping baby warm and snug.