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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]
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. Human embryology is the study of this development during the first eight weeks after fertilization.
In human pregnancy, prenatal development is also called antenatal development. The development of the human embryo follows fertilization, and continues as fetal development. By the end of the tenth week of gestational age, the embryo has acquired its basic form and is referred to as a fetus. The next period is that of fetal development where ...
During continued fetal development, the early body systems, and structures that were established in the embryonic stage continue to develop. Sex organs begin to appear during the third month of gestation. The fetus continues to grow in both weight and length, although the majority of the physical growth occurs in the last weeks of pregnancy.
The fetus reaches a length of about 40–48 cm (16–19 in). The fetus weighs about 2.5 to 3 kg (6 lb 10 oz)to 6 lb 12 oz). Lanugo begins to disappear. Body fat increases. Fingernails reach the end of the fingertips. A baby born at 36 weeks has a high chance of survival, but may require medical interventions. Fetus at 38 weeks after fertilization.
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.
Quickening indicates the start of fetal movements, usually felt 14–26 weeks after conception, or between the fourth and sixth month. [ 5 ] [ 6 ] A woman pregnant for the first time (i.e., a primigravida woman) typically feels fetal movements at about 20–21 weeks, whereas a woman who has given birth at least once will typically feel ...
The human fetus moves throughout its entire development. Fetal movement refers to motion of a fetus caused by its own muscle activity. Locomotor activity begins during the late embryological stage and changes in nature throughout development. Muscles begin to move as soon as they are innervated. These first movements are not reflexive, but ...