It seems a pity that an important issue like this becomes so emotive, and also that the thread becomes so full of simply untrue comments. I wanted to add my comments, from the point of view of a health professional, and also one who has considerable experinece in dealing with addictions.
I am afraid that it is a proven medical fact that smoking in pregnancy causes a variety of potential problems to the child, including lower birth rates on average, highre rates of prematurity, higher rates of cot death, and increased chance of repiratory illnesses later on. This are proven facts, and I could certainly point anyone who is interested to large, statistically valid, peer-reviewed studies in all these areas.
This does not mean that everyone who smokes in pregnancy is going to have these problems. Smoking increases the statistical liklihood of these things, it does not invariably lead to them. Quoting anecdotal evidence about people who smoked and did not have problems does not make any difference to this fact.
However, what also needs to be recognised is that addiction to nicotine IS an addiction, and the "choice" to smoke or not, for an addict, may be less of a choice than one would hope. The matter is being clouded here by peripheral issues, but that too is an indisputable fact. When one is addicted to something, justification of its use is PART of the addiction. It is entirely to be expected. Rationalising, passing judgement, threatening, cajoling: all will probably have limited effect. That is what is happening here.
I don't have any answers, but don't believe that mudslinging (from either side) is at all helpful.