  We discuss convergence issues as well as short distance constraints on the
deuteron wave functions based on chiral perturbation theory relevant to pion
deuteron scattering. Non-analytical terms arise in the multiple scattering
series for the pion-deuteron scattering length limiting the accuracy of the
calculations. This result resembles similar findings in the structure of the NN
interaction. The effects are found not to be numerically large. The iso-scalar
$\pi N $ scattering length from the iso-vector one and the $\pi d$ scattering
length yields values compatible with the experimental number and with much
smaller errors.
