A young mother is having difficulties understanding the function and importance of the placenta. She believes it provides a filter that only lets good stuff to the baby and keeps out all the bad stuff out. Because of this belief some of her decisions have not been very healthy for her or the fetus. How should the nurse approach this? What substances might the mother ingest that will cross the placental barrier? The mother has been cooperative with limiting her intake of potential teratogens; however at her 20th gestational week clinic visit she appears to be intoxicated. How should the nurse handle this?