I think it probably depends a great deal on the child; his overall health, his genetic endowments, AND his environment. My son inherited a risk of bronchial asthma from me, and my father; he suffered pneumonia at the age of 5; he lived in smoke for the first 9 yrs of his life. Removing the smoke from his environment produced immediate positive results, but he still has chronic bronchitis, and probably always will, and probably stands a substantial risk of developing adult-onset asthma, as I did, especially if he goes back to smoking.
I never considered it that big a risk, when he was younger, mainly because *I* lived in 2nd hand smoke all my childhood, and started smoking at the age of 13. But you know, I suffered severe sinus problems my whole life, and I figured they were just part of "me" -- but after I was smoke-free for about 2 or 2 1/2 months, for the FIRST TIME IN MY LIFE, I suddenly had clear sinuses. It felt strange to wake up with my sinuses and nose clear as a bell, and not to have to go around sniffing and blowing and snorting all the time; I can only attribute those long-standing problems to 2nd-hand smoke, and then 1st hand, after I started smoking. Of course it can never be known if I would have developed adult-onset asthma if I hadn't had that kind of 2nd hand and then 1st hand exposure to cigarette smoke, especially given the hereditary factors, but I'd say it's a very good possibility that I would not have.
I've also questioned a particular behavior that he suffered at about 3 wks of age -- just crying CONSTANTLY... I did not quit smoking when I was pregnant; in my 1st trimester, I was so nauseous that I cut down to about 3-4 cigs a day, but once the nausea was over, it slowly began to creep back up, till I was smoking just a bit less than a pk a day just before he was born, and I wonder now if that incessant crying at 3 wks was his own version of withdrawing from nicotine and the other alkaloids. It can never be known, obviously, but I do wonder. He started smoking when he was 18, and I have to wonder if he wasn't already predisposed to that choice and addiction, not only by the environment, his mom being a smoker for his whole life, but also by exposure to those chemicals
in utero. He quit a few years ago, thank heavens. Hope he stays that way, but if he feels like he needs to go back to smoking at any time, I've got an eRoll here, just waiting.
Andria