Look up some articles if you want to know the effects of smoking. You don't want to put anything into your body tat isn't good for either of you while you are pregnant. I don't know of any doctors who would encouraged you to continue smoking unless you are stressing out more from not smoking.
You need to worry about your own baby if shes not concerned about smoking while pregnant. Some people just don't get it, smoking AND second hand smoke is NOT OK for a baby. Your mom is right