In lieu of the report I just posted above, I thought I would paste this post from back in October that toughed upon this issue:

You will see from the post above (#36 in this string), there are women who just seem to lose interest in smoking when pregnant. It is interesting because some of these women lose all desire for cigarettes before they actually even knew they were pregnant, as if their bodies just knew not to smoke. Unfortunately, if these same women do not work on establishing good reasons to stay off of smoking, they often relapse shortly after delivery. Back in the days when smoking was allowed in hospitals, some of these women relapsed almost instantly. I used to joke about it in clinics, to illustrate how strong the desire would be to these women I would say that they almost asked for a cigarette before they would ask what was the sex of the baby. Many women in my groups nodded and said they knew exactly what I was saying from their past experiences.
So as I said to Tulip up above, while pregnancy may be the impetus for some women starting a quit, more ammunition needs to be developed and worked on for these women to sustain their quits. Long-term abstinences is going to require that the ex-smoker is truly sustaining his or her quit for himself or herself. You are the primary benefactor of your quit and to keep the benefits is as simple as always remembering to never take another puff!