I wonder this, too. It seems a lot of milestones are very much open to interpretation in terms of when they officially happened (ie sitting, walking, talking). In my mind, rolling over is one of the few that is definite.
My 4.5 month old can kinda sit (when I put her in the position) unsupported. She plants her arms out in front of her for support - I think I've heard this called the tripod position. For her baby book, I just made a note of this and I figure I'll add other dates as they happen (ie. when she no longer uses her arms for support, when she can get herself into that position on her own, etc).
Re: the technical definition of sitting up...
I wonder this, too. It seems a lot of milestones are very much open to interpretation in terms of when they officially happened (ie sitting, walking, talking). In my mind, rolling over is one of the few that is definite.
My 4.5 month old can kinda sit (when I put her in the position) unsupported. She plants her arms out in front of her for support - I think I've heard this called the tripod position. For her baby book, I just made a note of this and I figure I'll add other dates as they happen (ie. when she no longer uses her arms for support, when she can get herself into that position on her own, etc).