Fetus vs foetus

The spelling fetus is the preferred spelling in the medical world, regardless of location. It is used by virtually all biomedical journals. Therefore it is also the preferred spelling on Radiopaedia and we never use the spelling foetus. This latter spelling is still often used by lay-people in the United Kingdom, and many parts of the Commonwealth. Although even in these places the 'fetus' spelling is beginning to supersede the 'foetus' spelling.

Indeed the spelling fetus is the etymologically correct one as it derives from the Latin term 'fetus' meaning "offspring". The foetus usage is derived from the erroneous belief that the spelling fetus was an Americanism for which an original 'o' had been dropped.

By extension fetal and feticide are the correct spellings, and foetal and foeticide are not used.

By the same token the word fetor was mistakenly changed by the British to foetor and therefore we only use the former spelling on the site (e.g. fetor oris).

If foetus, foetal, etc are found on the site, they will be changed to fetus, fetal, etc.