  In this report I consider the cosmology of KK gravitinos in models with extra
dimensions, in particular in connection with the known non--standard high
energy regime of expansion which is associated with them. The main result is
that the production of such KK modes, once one considers BBN constraints on the
allowed entropy released in their decays, is not compatible with non--standard
expansion after inflation: there is no five--dimensional Planck mass for which
the produced KK gravitinos are safe with respect to BBN. This conclusion holds
for both flat and warped models in which only gravity propagates in the full
spacetime. This report is based on the work arXiv:0705.4227 [hep-ph].
