placental barrier

synonym: placental membrane
https://doi.org/10.1351/goldbook.11096

Multilayered membrane of fetal tissue within the placenta that separates the maternal blood from the fetal blood and allows selective passage of substances between the two.

Note: This membrane blocks only a few xenobiotics.
Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 793 [Terms] [Paper]