Fetus

The unborn offspring from the end of the 8th week after conception (when the major structures have formed) until birth. Up until the eighth week, the developing offspring is called an embryo.

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1. The unborn young of a viviparous animal following the embryonic period. 2. [NA] In humans, the product of conception from the end of the eighth week to the moment of birth. [L. offspring]

- f. in fetu condition in which a small, imperfectly formed f. is contained within a f..

- harlequin f. a severe autosomal recessive form of collodion baby in a newborn, usually premature, infant; i.e., a form of ichthyosiform erythroderma characterized by encasement of the body in grayish brown, often fissured plaques resembling plates of armor and by grotesque deformity of the face with eclabium and gangrene of terminal phalanges; usually fatal within a few days, although treatment with 13-cis-retinoic acid has been successful in some cases. SYN: ichthyosis fetalis (1).

- impacted f. a f. which, because of its large size or narrowing of the pelvic canal, has become wedged and incapable of spontaneous advance or recession.

- f. papyraceus one of twin fetuses that has died and been pressed flat against the uterine wall by the growth of the living f..

- f. sanguinolentis (san-gwi′no-len′tis) dead f. that has become macerated.

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fe·tus or chiefly Brit foe·tus 'fēt-əs n, pl fe·tus·es or chiefly Brit foe·tus·es or foe·ti 'fēt-.ī an unborn or unhatched vertebrate esp. after attaining the basic structural plan of its kind specif a developing human from usu. two months after conception to birth compare EMBRYO

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n.

a mammalian embryo during the later stages of development within the uterus. In human reproduction it refers to an unborn child from its eighth week of development.

• fetal adj.

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fe·tus (feґtəs) [L.] the unborn offspring of any viviparous animal; specifically, the unborn offspring in the postembryonic period, after major structures have been outlined, in humans from nine weeks after fertilization until birth. Cf. embryo.