We study the effects of strong magnetic fields (B ≳ 10¹³ G) in the cross section for ν_enpe scattering in the presence of a degenerate electron background. This can be relevant for the ν_e propagation in the proto--neutron star stage after supernovae collapse. We find that for field strengths B ≳ 10¹⁶ G(E_ν/10 MeV)² the ν_e opacity is sizeably affected by the magnetic field and can lead to a shift in the location of the electron neutrino sphere towards lower densities. We discuss the implications that this may have for scenarios proposed to explain the observed pulsar velocities.