Definition of placental in US English:



  • 1Relating to a placenta.

    • ‘We applaud stem-cell research, especially with adult cells, and placental and umbilical tissues.’
    • ‘Infection of humans usually occurs by inhalation of these organisms from air that contains airborne barnyard dust contaminated by dried placental material, birth fluids, and excreta of infected herd animals.’
    • ‘In mice, the gender of adjacent siblings on the placental fetus line in the uterus will affect such things as the male/female ratio of a given mouse's subsequent offspring, and even the longevity of those offspring.’
    • ‘I would like to see more about the possibility of using the placental and adult stem cells vs. the embryonic ones.’
    • ‘The couple, from Whinmoor, Leeds, claim greater care should have been taken of the woman who was diagnosed with pre-eclampsia - a placental defect - some weeks before the birth.’
    • ‘None of the women with PAPP-A values in the top 60% had stillbirths caused by placental problems.’
    • ‘She believes her 14-year-old daughter's scleroderma, a systemic sclerosis, is linked to silicone crossing the placental barrier.’
    1. 1.1Zoology Relating to or denoting mammals that possess a placenta; eutherian.
      • ‘The quagga is a placental mammal, a group also called Eutheria by scientists.’
      • ‘To distinguish them from the marsupials and the placental mammals the monotremes are placed in their own class, the prototheria.’
      • ‘The reproductive system of the therians (marsupial and placental mammals) is a complex variation on the egg-layer's basic tubular structure.’
      • ‘Both taxa are placental or eutherian mammals, but their relationships to other eutherians continue to be a source of discussion.’
      • ‘There are several cases of convergent evolution between marsupials and placental mammals, in which the two animals have evolved to fill the same ecological niche in different parts of the world.’


  • A placental mammal.

    • ‘An unquestioned monotreme, Steropodon has molars that are surprisingly similar to those of marsupials and placentals, suggesting a closer relationship to living therians than had generally been thought.’
    • ‘Cathy's work suggests that, unlike placentals, marsupial mammals never had to rediscover red; for them, it's always been there.’
    • ‘Split of therians into placentals and marsupials happens at this time.’
    • ‘‘Looking across the world, 99.9 percent of modern mammals are placentals and marsupials, so finding how they came about is an important question,’ he said.’
    • ‘It is significant because a vast majority of mammals alive today are placentals.’