A maternal facing structure of the placental disc, adjacent to the intervillous space. Major components of the placental basal plate include decidua basalis, fibrinoid, connective tissue, extravillous trophoblasts, and residues of degenerating villi and maternal vessels. [ http://www.ncbi.nlm.nih.gov/pubmed/32108320 http://www.ncbi.nlm.nih.gov/pubmed/17059842 ]