  We present Raman measurements on the iron-pnictide superconductors
CeFeAsO_{1-x}F_{x} and NdFeAsO{1-x}F_{x}. Modeling the Fe-As plane in terms of
harmonic and a cubic anharmonic Fe-As interaction we calculate the temperature
dependence of the energy and lifetime of the Raman active Fe B_{1g} mode and
fit to the observed energy shift. The shifts and lifetimes are in good
agreement with those measured also in other Raman studies which demonstrate
that the phonon spectrum is well represented by phonon-phonon interactions
without any significant electronic contribution. We also estimate the
anharmonic expansion from Fe (56->54) isotope substitution to \Delta a=5.1
10^{-4}\AA and \Delta d_{Fe-As}= 2.510^{-4}\AA and the shift of harmonic zero
point fluctuations of bond lengths <\Delta x^2><=3 10^{-5}\AA^2, giving a total
relative average decrease of electronic hopping integrals of |\delta t|/t<= 2.0
10^{-4}. The results poses a serious challenge for any theory of
superconductivity in the pnictides that does not include electron-phonon
interactions to produce a sizable Fe-isotope effect.
