  The usual theoretical treatments of the near-threshold $pp \rightarrow
pp\pi^0$ reaction are based on various phenomenological Lagrangians. In this
work we examine the relationship between these approaches and a systematic
chiral perturbation method. Our chiral perturbation calculation indicates that
the pion rescattering term should be significantly enhanced as compared with
the traditional phenomenological treatment, and that this term should have
substantial energy and momentum dependence. An important consequence of this
energy-momentum dependence is that, for a representative threshold kinematics
and within the framework of our semiquantitative calculation, the rescattering
term interferes destructively with the Born-term in sharp contrast to the
constructive interference obtained in the conventional treatment. This
destructive interference makes theoretical cross sections for $pp \rightarrow
pp\pi^0$ much smaller than the experimental values, a feature that suggests the
importance of the heavy-meson exchange contributions to explain the
experimental data.
