Lily is still just fitting into mediums, she's 10 months now not sure on weight but she's not a big girl. I'd get a medium, I dont tend to add extra inserts to them but they do last quite a while unless she's teething I think.
I'm thinking about selling on our mediums as they are beginning to get a little difficult to put on.
Only thing with these is the elastic stretches terribly in the wash as the weight from the aio bit pulls on them, I have to put them in their own net bagto wash, so they arent that easy really, they really can be a pita for washing, take ages to dry and dont look that new for long, again due to the washing. Grrr it really bugs me that bumgenius can't sort this.
Sour point there