Without a vascular structure in the uterus or womb of most mammals that provides oxygen and nutrients for and the transfer of wastes from the developing fetus (unborn baby): "Aplacental mammals do not have the placental organ that other mammals have; for example, Monotremes (primitive egg-laying mammals living in Australia and New Guinea and consisting of the platypus and the echidna or spiny anteater) and marsupials (kangaroos, wallabies, opossums, koalas, and wombats); all the mothers of which have pouches to hold their young and are categorized as being aplacental creatures."

"To repeat for a better understanding, the placenta is a splecialized organ within the womb of the mother that brings the bloodstream of the fetus into close contact with the bloodstream of the mother. Food, water, and oxygen pass across from the mother to the child, and wastes passover to the mother's blood and are carried away; so, the aplacental mammals mentioned in the paragraph above produce their babies without the placental system."