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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]
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.
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 .
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 this stage, a fetus is about 30 mm (1.2 inches) in length, the heartbeat is seen via ultrasound, and the fetus makes involuntary motions. [47] 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.
There is no sharp limit of development, gestational age, or weight at which a human fetus automatically becomes viable. [13] According to one study, between 2013 and 2018 at United States academic medical centers, the percentage of newborns who survived long enough to leave the hospital was 30% at 22 weeks, 55% at 23 weeks, 70% at 24 weeks, and ...
Diogenes recognized that the placenta was a nutritional source for the growing fetus. He also said that the development of males took four months, but that the development of females took five months. He did not think the embryo was alive. Alcmaeon also made some contributions, and he is the first person reported to have practiced dissection.
At 20 weeks, the fetus is able to implement feedback mechanisms for the production of thyroid hormones. During fetal development, T 4 is the major thyroid hormone being produced while triiodothyronine (T 3) and its inactive derivative, reverse T 3, are not detected until the third trimester. [2]