What is the miscarriage rate for pregnant woman that smoked salvia?

I doubt that there have been studies on the effects of salvia on pregnant women and their unborn babies. Attempting to find a reliable number for your question is next to impossible. Also, many variables need to be known in order to make an educated guess on how severly the unborn baby will be effected. These variables include how much of the drug was used, how often the drug was used, and how far into the pregnancy the drug was used.