I think its completely healthy from birth if practiced safely. (no smoking, drinking, heavy covers, toddlers in bed, risk of falling between cracks, or an obese parent, etc.) Babies bodies react to their parents cues, even subtle. CoSleeping can cure fevers, and many studies prove it reduces the risk of SIDS.
I also think its perfectly healthy because can give the parent more sleep, which creates a rested and functioning daytime parent.
I do not think co sleeping or bedsharing is the right way for every type of family. I cosleep now, but my first child slept in his own crib from an early age. It was what worked for us at that point, and with our second, now cosleeping works very well.
at 3:29 AM on Dec. 4, 2010