Definition of placenta in US English:



  • 1A flattened circular organ in the uterus of pregnant eutherian mammals, nourishing and maintaining the fetus through the umbilical cord.

    The placenta consists of vascular tissue in which oxygen and nutrients can pass from the mother's blood into that of the fetus, and waste products can pass in the reverse direction. The placenta is expelled from the uterus at the birth of the fetus, when it is often called the afterbirth. Marsupials and monotremes do not develop placentas

    • ‘It most likely functions as an adhesion protein, connecting the placenta to the uterus.’
    • ‘In most pregnant women, the placenta forms and grows just as it should.’
    • ‘Causes of spontaneous abortion may relate to the fetus, the placenta, or the uterus.’
    • ‘New alternatives, which are currently experimental, include harvesting stem cells from umbilical cord blood or placentas of new born babies.’
    • ‘The placenta connects the baby's blood supply to the mother's blood.’
    • ‘Folic acid also is crucial to support the rapid growth of the placenta and fetus.’
    • ‘We felt that compared with placentas with focal lesions, placentas with well-established HEV would more reliably reflect associated events.’
    • ‘These help to anchor it to the lining of the uterus and will eventually grow into the placenta, the organ that feeds and protects the baby until birth.’
    • ‘Transplanting cord blood stem cells from placenta and umbilical cords have the same effect as a bone-marrow transplant.’
    • ‘The baby is connected to the umbilical cord, the umbilical cord to the placenta, and the placenta to the mother, at least at this stage of the proceedings.’
    • ‘The sonographer scans the patient, taking an initial assessment of the fetuses, the placenta, and the amniotic cavity.’
    • ‘He explores how cocaine destroys the placenta, the fetus, and the infant's life.’
    • ‘Placenta accreta is a placenta that implants too deeply and too firmly into the uterine wall.’
    • ‘Chorioangiopagus vessels are vessels that join the fetuses in the placenta.’
    • ‘We analyzed tissues from 368 specimens of pregnancy loss and 219 placentas of live-born infants using CGH.’
    • ‘Alcohol enters the fetus readily through the placenta and is eliminated by maternal metabolism.’
    • ‘The mother had an aggressive metastatic disease, and the cancer could have spread across the placenta to the fetus.’
    • ‘This transformation is essential to ensure a normal blood supply to the fetus and placenta throughout pregnancy.’
    • ‘She could also transmit the infection to the fetus across the placenta.’
    • ‘In each later pregnancy, maternal Rh antibodies can cross the placenta and reach the fetus.’
  • 2Botany
    (in flowers) part of the ovary wall to which the ovules are attached.

    • ‘Partial view of flower and dissected gynoecium with two placentas.’
    • ‘As the ovary elongates only above the placenta, the ovules appear basal at anthesis.’
    • ‘In both species the gametophytic cells of the placenta generally have less prominent wall labyrinths than sporophytic cells.’
    • ‘The entire placenta with attached ovules was removed via a longitudinal incision in the ovary wall.’
    • ‘The ovary has axile intruded placentae with around 250-350 ovules.’


Late 17th century: from Latin, from Greek plakous, plakount- ‘flat cake’, based on plax, plak- ‘flat plate’.