med. jur. The unborn child. The name of embryo is sometimes given to it; but, although the terms are occasionally used indiscriminately, the latter is more frequently employed to designate the state of an unborn child during the first three months after conception, and by some until quickening. A foetus is sometimes described by the uncouth phrase of infant in ventre sa mere. 2. It is sometimes of great importance, particularly in criminal law, to ascertain the age of the foetus, or how far it has progressed towards maturity. There are certain signs which furnish evidence on this subject, the principal of which are, the size and weight, and the formation of certain parts as the cartilages, bones These are not always the same, much of course must depend upon the constitution and health of the mother, and other circumstances which have an influence on the foetus.