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Prenatal development (from Latin natalis 'relating to birth') involves the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization , in the germinal stage of embryonic development, and continues in fetal development until birth .
Gestational age: 9 weeks and 0 days until 11 weeks and 6 days old. Embryonic age: 7 weeks and 0 days until 9 weeks and 6 days old. Fetus at 10 weeks. Embryo measures 30–80 mm (1.2–3.1 in) in length. Ventral and dorsal pancreatic buds fuse during the 8th week; Intestines rotate. Facial features continue to develop. The eyelids are more ...
Fetal viability refers to a point in fetal development at which the fetus may survive outside the womb. The lower limit of viability is approximately 5 + 3 ⁄ 4 months gestational age and is usually later. [20] There is no sharp limit of development, age, or weight at which a fetus automatically becomes viable. [21]
Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages. At the beginning of the ninth week, the embryo is termed a fetus (spelled "foetus" in British English). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs.
At the end of a month it is hardened, in two months the head is formed". [9] In Indian literature, the start of consciousness in an embryo is not clearly defined. Some scriptures state that it is active at conception, while others suggest that consciousness begins in the seventh to ninth month of fetal development.
An explorative study found, however, that 3- to 5-month-old infants can be taught independent standing, which was considered safe. [32] Passes objects between hands. [31] Some infantile reflexes, such as the palmar grasp reflex, go away. [31] Grabs objects using a raking grasp, where fingers rake at objects to pick them up. [31]
The embryonic period varies from species to species. In human development, the term fetus is used instead of embryo after the ninth week after conception, [19] whereas in zebrafish, embryonic development is considered finished when a bone called the cleithrum becomes visible. [20]
A fetus is a stage in the human development considered to begin nine weeks after fertilization. [4] [5] In biological terms, however, prenatal development is a continuum, with many defining features distinguishing an embryo from a fetus. A fetus is also characterized by the presence of all the major body organs, though they will not yet be ...