Abstract
A possible relationship between stability of a tetracycline and persistence in the foetal skeleton is discussed; it seems that the greater the stability of a tetracycline, the more it may interfere with bone-forming processes. Therefore, assuming that limited instability does not impair antibiotic potency in vivo, the use of a low-stability tetracycline seems to be a safer form of treatment in order to avoid undesired effects on the foetal skeleton.