Quoting Mama Lizzy :]:" I quit cold Turkey after smoking for four years....I was definitely under a lot of stress/ depression ... [snip!] ... comes down to will power....I was scared to death of harming my baby....as soon as that test showed positive I couldn't do it."
I have to disagree on the will power part. Smokers are psychically addicted. Some can handle the after effects while others cannot.
I don't think anyone wants to "harm" their unborn child. Those who smoke during pregnancy do not think "Hmm, maybe I should light up today so I can poison my fetus". It's an addiction and if it were that easy to quit the average smoker wouldn't take at least 6 tries to finally quit.