Definition of fetus in US English:


(British foetus)

nounPlural fetuses

  • An unborn offspring of a mammal, in particular an unborn human baby more than eight weeks after conception.

    • ‘Doctors in China will harvest cells taken from aborted human foetuses which will then be injected into Mr Bell's head and spinal cord.’
    • ‘Those who favour abortion cannot accept that a foetus is a human being, exactly the same as a new born baby is a human being.’
    • ‘Use a barrier contraceptive the first month: female fetuses may be adversely affected.’
    • ‘Alcohol enters the fetus readily through the placenta and is eliminated by maternal metabolism.’
    • ‘Feedback is currently being used in a trial of early versus delayed delivery for preterm, growth retarded fetuses.’
    • ‘Developing fetuses, pregnant women, and young children are especially vulnerable.’
    • ‘It was perceived that they were the African women who could carry a fetus to full term.’
    • ‘Poorly controlled asthma can lead to serious medical problems for pregnant women and their fetuses.’
    • ‘The youngest fetus with Down's syndrome in our sample was 22 weeks old at the time of measuring.’
    • ‘However, fewer than one percent of fetuses become infected when their mother has a recurrent infection.’
    • ‘Further pregnancies should then pose no risk to the fetus or mother.’
    • ‘How well a woman and the fetus do during pregnancy depends upon the type of heart problem.’
    • ‘A small subset of fetuses with large lung lesions will become hydropic, deteriorate rapidly, and die in utero.’
    • ‘After the eighth week of pregnancy, the developing baby is called a foetus.’
    • ‘Already cloning embryos, using aborted foetuses, gene swapping and gene therapy will mean the long term impacts will be immense on our everyday living.’
    • ‘Not every mother agrees that it is desirable to identify and terminate a fetus with Down's syndrome.’
    • ‘The woman is likely to be concerned about the risk of medication to the fetus.’
    • ‘Some men have even tried to prevent women having abortions on grounds that the unborn foetus belongs to them.’
    • ‘The past 20 years have seen rapid advances in the detection of genetic disorders in human fetuses.’
    • ‘It just happens that she helps a lot of women to abort their unborn fetuses.’
    embryo, fertilized egg, unborn baby, unborn child
    View synonyms


The spelling foetus has no etymological basis but is recorded from the 16th century and until recently was the standard British spelling in both technical and nontechnical use. In technical usage, fetus is now the standard spelling throughout the English-speaking world


Late Middle English: from Latin fetus ‘pregnancy, childbirth, offspring’.