  The nucleon-nucleon scattering in a large magnetic background is considered
to find its potential to change the neutrino emissivity of the neutron stars.
For this purpose we consider the one-pion-exchange approximation to find the NN
cross-section in a background field as large as
$10^{15}\texttt{G}-10^{18}\texttt{G}$. We show that the NN cross-section in
neutron stars with temperatures in the range 0.1-5 \texttt{MeV} can be changed
up to the one order of magnitude with respect to the one in the absence of the
magnetic field. In the limit of the soft neutrino emission the neutrino
emissivity can be written in terms of the NN scattering amplitude therefore the
large magnetic fields can dramatically change the neutrino emissivity of the
neutron stars as well.
