A preliminary exploration of epigenetic regulation on placental P-gp. SAHA/TSA reduced total HDAC activity and HDAC1/2/3 expression in Bewo and JAR. SAHA/TSA induced P-gp expression in Bewo and JAR. There was a negative relationship between HDAC1/2 and ABCB1 mRNA expression. The findings may provide references for safe pharmacotherapy during pregnancy.