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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.
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 .
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]
Drawing of a fetus in utero. Gestation is the period of development during the carrying of an embryo , and later fetus , inside viviparous animals (the embryo develops within the parent). [ 1 ] It is typical for mammals , but also occurs for some non-mammals.
Once the fetus is sufficiently developed, chemical signals begin the process of birth, which begins with the fetus being pushed out of the birthing canal. The newborn, which is called an infant in humans, should typically begin respiration on its own shortly after birth. Not long after, the placenta eventually falls off on its own.
Learning language as an infant also requires fetal memory. It is now known that the mother's voice is clearly heard from inside the womb and that the fetus can differentiate speech sounds, particularly the phonemes (a single segment of sound) in speech. This is evident in the baby when born, showing many signs of early language comprehension.
This activity assists with proper joint development. [15] Women who have already given birth have more relaxed uterine muscles that are consequently more sensitive to fetal motion, and for them fetal motion can sometimes be felt as early as 14 weeks. [18] By about week 21, the fetus begins to develop a regular schedule of movement. [17]
In the Womb is a documentary television special miniseries that was premiered on March 6, 2005, on the National Geographic Channel.Originally beginning as a special about human pregnancy (titled Life Before Birth in the UK), the program features the development of embryos in the uterus of various animal species.