Cigarette

What substance in cigarette will be harmful to our digestiv system? Does its byproducts, Tar, Nicotine and Carbon monoxide or others that will cause babies born by smoking mother with lower body weight on average and higher chance of death?
To answer the above questions:
(1) Nearly all the byproducts of smoking cigarette will not be directly harmful to our digestive system but being harmful to the autonomic nervous system, and both of the parasympathetic and the sympathetic nerves. Thus, the pupils of the eyes are first constricted and then dilated. As far as we know that smoking is mostly harmful to our respiratory system e.g. lungs, trachea, bronchi;
(2) As far as smoking mother being concerned, it might be due to the harmful effects of nicotine on certain nervous systems and as the result, the average body weight of babies will be lower and the chance of death being higher.

I think that three of them will cause harm to our digestive system.
Tar and nicotine will cause babies born to have lower weights,and also higher decline rate.
If u want more info,just to buy a reference Biology book about this topic.
U may get what u want.