Hi there,

Yes, if they're old enough to have worn/bald spots then that will definetly affect the usage as they'll be much less absorbant than they were when they were newer. If that's the case then that means that at the bald spots there's only the polyester base of the fabric and the cotton has been worn away...

That said, they're not totally unuseable if you're at all crafty and frugal, especially if the elastic is still in reasonable shape. You could use a small prefold (preemie or infant size would fit nicely without adding too much bulk) or a liner (snap-in would be convenient but not strictly necessary) in them to boost the absorbancy. You could also sew some fabric inside and/or outside to boost the absorbancy. I remember someone on the board sewing some absorbant fabric on the outside of the diaper and sewing some cute prints on top of that so that the diaper turned out totally adorable and just as functional! 

You could even try them out as is to see if they could be used for times when you won't need much absorbancy, just depends how many worn spots there are and how heavy a wetter you have. Newborns rarely need much absorbancy as they have such frequent bowel movements and need frequent changes.

Karen.