I recently received this email from one of my readers:

I am about to be a father and have been told that you have done research on the effects of marijuana use during pregnancy on a child. I would like to know where I can find and read whatever has been published about these studies.

The topic of marijuana use in pregnancy is a very confusing one, mainly because marijuana does not have a direct health effect on pregnancy; there is no increased rate of preterm labor, growth retardation, or other such complications. However—and this is a big however—even though marijuana does not affect pregnancy outcome, it does have an impact on fetal brain development.  Long-term studies document that children whose mothers have used marijuana during pregnancy have a higher rate of executive functioning difficulties, which interfere with learning and behavior, especially as related to planning and following through with a task. Executive functioning is a vital issue, because although the children "look normal," they cannot behave and respond appropriately in the classroom or sometimes even at home. For a fuller discussion of executive functioning, see my previous blog on this topic.