We know there are things that may increase or decrease IQ. Children who were breastfed have a slightly higher IQ. Iodine is important for development. The people in areas of the world that don't have natural iodine in food also have lower IQs. When iodine was added to their diet during development, the IQ went up in those same areas. Coastal areas, where children were fed fish high in mercury had lower IQs than the same group of children inland. I have to imagine that taking drugs while pregnant could be doing some serious, irreversible damage. We know that excessive alcohol intake during pregnancy produces similar damage in the offspring regardless of which group is doing it.