This is the author's accepted manuscript, post peer review. For the published version, please see the link in this record.The use of pharmaceuticals during pregnancy is often a necessity for the health of the mother. Until recently, the placenta was viewed as a passive organ through which molecules are passed indiscriminately between mother and fetus. In reality, the placenta contains a plethora of transporters, some of which appear to be specifically dedicated to removal of xenobiotics and toxic endogenous compounds. Drug efflux transporters such as P-glycoprotein (P-gp), several multidrug resistant associated proteins (MRPs) and breast cancer resistant protein (BCRP) may provide mechanisms that protect the developing fetus. Bile acid transporters may also play a role in exporting compounds back into the maternal compartment. Steroid hormones directly influence the level of expression and function in some of these transporters. Investigating the link between the hormones of pregnancy and these drug efflux transporters is one possible key in developing strategies to deliver drugs to the mother with minimal fetal risk.This research was supported by NIH grants P01HD-3-9878 and N01DA-4-7405
