My premature newborn son passed away 18 years ago and was buried in a wooden coffin. I am about to relocate and want to exhume his remains to be cremated. I need to know how long does it take for a premature newborn body to decompose and will I find any remains left to cremate?

Newborn bones are, at best cartilaginous bones meaning they have not caclified yet. In all due respect, there wouldn't be very much left of your baby to cremate as the cartilaginous bones would deteriorate rapidly after incarceration.

I would be hesitant to disturb last remains, let your son rest in peace under the circumstances.