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A fetus or foetus (/ˈfiːtəs/; pl.: fetuses, foetuses, rarely feti or foeti) is the unborn mammalian offspring that develops from an embryo.[1] Following the embryonic stage, the fetal stage of development takes place. Prenatal development is a continuum, with no clear defining feature distinguishing an embryo from a fetus. However, a fetus is characterized by the presence of all the major body organs, though they will not yet be fully developed and functional, and some may not yet be situated in their final anatomical location.
In human prenatal development, fetal development begins from the ninth week after fertilization (eleventh week gestational age) and continues until the birth of a newborn.
- ^ Ghosh, Shampa; Raghunath, Manchala; Sinha, Jitendra Kumar (2017), "Fetus", Encyclopedia of Animal Cognition and Behavior, Springer International Publishing, pp. 1–5, doi:10.1007/978-3-319-47829-6_62-1, ISBN 9783319478296