  We evaluate the modifications to the cosmic microwave background anisotropy
spectrum that result from a semiclassical expansion of the Wheeler-DeWitt
equation. Recently, such an investigation in the case of a real scalar field
coupled to gravity, has led to the prediction that the power at large scales is
suppressed. We make here a more general analysis and show that there is an
ambiguity in the choice of solution to the equations describing the quantum
gravitational effects. Whereas one of the two solutions describes a suppression
of power, the other one describes an enhancement. We investigate possible
criteria for an appropriate choice of solution. The absolute value of the
correction term is in both cases of the same order and currently not
observable. We also obtain detailed formulae for arbitrary values of a complex
parameter occurring in the general solution of the nonlinear equations of the
model. We finally discuss the modification of the spectral index connected with
the power spectrum and comment on the possibility of a quantum-gravity induced
unitarity violation.
