Is there any way to lessen the effects of smoking on my pregnancy?

Yes. Quitting, or at least cutting down, is the only way to lessen the effects.
Yes. It is best to avoid smoking whether pregnant or not. Smoking has deleterious effects both on the unborn baby as well as the newborn, infant, and beyond. Many quit options are available. If quitting is not possible, then perhaps the gum or patch may be considered.