  The $d(e,e'\pi^+)$ reaction in the parallel kinematics has been investigated
using a dynamical model of pion electroproduction on the nucleon. A unitary
$\pi NN$ model has been used in order to examine the effects due to the final
two-nucleon interactions, pion rescattering from the second nucleon, and the
intermediate $NN$ and $N\Delta$ interactions. It has been found that these $\pi
NN$ mechanisms are small, but they can have significant contributions to the
$d(e,e'\pi^+)$ cross sections through their interference with the dominant
impulse term. For the longitudinal cross sections, the effects due to the
interference between the pion pole term and other production mechanisms are
also found to be very large. Our findings clearly indicate that these
interference effects must be accounted for in any attempt to determine from the
$d(e,e'\pi^+)$ data whether the pion form factor and/or $\pi NN$ vertex of the
pion pole term are modified in the nuclear medium.
