Smoking and drinking while pregnant is generally acknowledged to be a bad for the child's health depending, of course, on the extent of it. So how common is it and what are some of the predictors?
Using Growing Up in Ireland data I graph the mothers response to a question which asked about this. About 60% never drank and less than 40% said occasionally. For smoking about 75% never smoked though about 13% smoked daily.
These questions were asked 9 years after the child was born and are probably under-estimates. One is less likely, I think, to overstate one's drinking or smoking.
If one does some simple multivariate (ordered probit) analysis it is striking that there are some very different patterns:
Older mothers are more likely to have consumed alcohol than younger mothers while pregnant but young mothers are more likely to smoke than the older ones. Income also has opposite effects being positively associated with drinking and negatively associated with smoking. The same is true for mothers education. Likewise medical card holders are more (less) likely to smoke (drink). So there seems to be a clear class divide. These effects are simultaneous, remember.
The one factor I found which had a consistent effect (& there are many other possible factors which I didn't look at) was a question that asked the respondent "Would you describe yourself as religious/spiritual?". Those that answered in the higher categories ("very much so" or "extremely") were significantly less likely to have smoked or drank alcohol while pregnant.
It is interesting to speculate whether this has something to do with an association between religiousity and discount rates. It seems there may be positive externalities from religion/spirituality.