An anatomical space that separates the basal plate and the chorionic plate. The intervillous space is filled with endometrial gland secretions during early stages of the pregnancy and later perfused with maternal blood, bathing the chorionic villous tree. [ doi:10.1007/978-3-030-84725-8 http://www.ncbi.nlm.nih.gov/pubmed/32108320 ]