  Recent work in the literature has found a suppression or, instead, an
enhancement of the Cosmic Microwave Background power spectrum in quantum
gravity, although the effect is too small to be observed, in both cases. The
present paper studies in detail the equations recently proposed for a
Born-Oppenheimer-type analysis of the problem. By using a perturbative approach
to the analysis of the nonlinear ordinary differential equation obeyed by the
two-point function for scalar fluctuations, we find various explicit forms of
such a two-point function, with the associated power spectrum. In particular, a
new family of power spectra is obtained and studied. The theoretical prediction
of power enhancement at large scales is hence confirmed.
