Fetus
A fetus (pronounced /ˈfiːtəs/; also spelled foetus, fœtus, faetus, or fætus, see below) is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.
In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization. Weeks 9 to 16Fetus attached to placenta, approximately 12 weeks after fertilization.The fetal stage commences at the beginning of the 9th week. At the start of the fetal stage, the fetus is typically about 30 millimetres (1.2 in) in length from crown to rump, and weighs about 8 grams. The head makes up nearly half of the fetus' size. Breathing-like movement of the fetus is necessary for stimulation of lung development, rather than for obtaining oxygen. The heart, hands, feet, brain and other organs are present, but are only at the beginning of development and have minimal operation.
Fetuses are not capable of feeling pain at the beginning of the fetal stage, and may not be able to feel pain until the third trimester. At this point in development, uncontrolled movements and twitches occur as muscles, the brain and pathways begin to develop.
Weeks 16 to 25A woman pregnant for the first time (i.e. a primiparous woman) typically feels fetal movements at about 21 weeks, whereas a woman who has already given birth at least two times (i.e. a multiparous woman) will typically feel movements by 20 weeks. By the end of the fifth month, the fetus is about 20 cm (8 inches).
Weeks 26 to 38Artist's depiction of fetus at 40 weeks after fertilization, about 20 inches (51 cm) head to toe.The amount of body fat rapidly increases. Lungs are not fully mature. Thalamic brain connections, which mediate sensory input, form. Bones are fully developed, but are still soft and pliable. Iron,calcium, and phosphorus become more abundant. Fingernails reach the end of the fingertips. The lanugobegins to disappear, until it is gone except on the upper arms and shoulders. Small breast buds are present on both sexes. Head hair becomes coarse and thicker. Birth is imminent and occurs around the 40th week. The fetus is considered full-term between weeks 37 and 40, which means that the fetus is considered sufficiently developed for life outside the uterus. It may be 48 to 53 cm (19 to 21 inches) in length, when born. Control of movement is limited at birth, and purposeful voluntary movements develop all the way until puberty
In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization. Weeks 9 to 16Fetus attached to placenta, approximately 12 weeks after fertilization.The fetal stage commences at the beginning of the 9th week. At the start of the fetal stage, the fetus is typically about 30 millimetres (1.2 in) in length from crown to rump, and weighs about 8 grams. The head makes up nearly half of the fetus' size. Breathing-like movement of the fetus is necessary for stimulation of lung development, rather than for obtaining oxygen. The heart, hands, feet, brain and other organs are present, but are only at the beginning of development and have minimal operation.
Fetuses are not capable of feeling pain at the beginning of the fetal stage, and may not be able to feel pain until the third trimester. At this point in development, uncontrolled movements and twitches occur as muscles, the brain and pathways begin to develop.
Weeks 16 to 25A woman pregnant for the first time (i.e. a primiparous woman) typically feels fetal movements at about 21 weeks, whereas a woman who has already given birth at least two times (i.e. a multiparous woman) will typically feel movements by 20 weeks. By the end of the fifth month, the fetus is about 20 cm (8 inches).
Weeks 26 to 38Artist's depiction of fetus at 40 weeks after fertilization, about 20 inches (51 cm) head to toe.The amount of body fat rapidly increases. Lungs are not fully mature. Thalamic brain connections, which mediate sensory input, form. Bones are fully developed, but are still soft and pliable. Iron,calcium, and phosphorus become more abundant. Fingernails reach the end of the fingertips. The lanugobegins to disappear, until it is gone except on the upper arms and shoulders. Small breast buds are present on both sexes. Head hair becomes coarse and thicker. Birth is imminent and occurs around the 40th week. The fetus is considered full-term between weeks 37 and 40, which means that the fetus is considered sufficiently developed for life outside the uterus. It may be 48 to 53 cm (19 to 21 inches) in length, when born. Control of movement is limited at birth, and purposeful voluntary movements develop all the way until puberty