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Encyclopedia > Fetus
Human fetus at eight weeks. A small part of the placenta is shown at the bottom, while the fluid-filled amnion surrounds it.
Human fetus at eight weeks. A small part of the placenta is shown at the bottom, while the fluid-filled amnion surrounds it.

A fetus (or foetus or fœtus) is a developing mammal or other viviparous vertebrate, after the embryonic stage and before birth. The plural is fetuses, or sometimes feti. The fetal stage of prenatal development starts when the major structures have formed, and lasts until birth.[1] Fetus or Foetus may refer to: Fetus, a stage in mammalian development Foetus (band) Category: ... From Henry Gray (1821–1865). ... From Henry Gray (1821–1865). ... For the alien race in Stephen Donaldsons The Gap Cycle, see Amnion (Gap Cycle). ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... A viviparous animal is an animal employing vivipary, a method of reproduction in which the embryo develops inside the body of the mother from which it gains nourishment, and not from an egg. ... This article does not cite any references or sources. ... For other uses, see Embryo (disambiguation). ... Parturition redirects here. ... This article is about prenatal development in humans. ...


In humans, the fetal stage of prenatal development starts at approximately the beginning of the 9th week after fertilization, or the eleventh week in "gestational age."[2][3] This article is about prenatal development in humans. ... Categories: Biology stubs ... Gestational age is age of a fetus (or newborn infant) from presumed conception. ...

Contents

Etymology and spelling variations

The word fetus is from the Latin fetus, meaning offspring, bringing forth, hatching of young.[4] It has Indo-European roots related to sucking or suckling.[5] For other uses, see Latin (disambiguation). ... The Proto-Indo-European language (PIE) is the hypothetical common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans. ... A breastfeeding infant Breastfeeding is the practice of a woman feeding an infant (or sometimes a toddler or a young child) with milk produced from her mammary glands, usually directly from the nipples. ...


Foetus is an English variation on the Latin spelling, and has been in use since at least 1594, according to the Oxford English Dictionary, which describes "fetus" as "etymologically preferable ... but in actual use ... almost unknown", and gives foetus as the standard spelling. The variant foetus or fœtus may have originated with an error by Saint Isidore of Seville, in AD 620.[6] The preferred spelling in the United States is fetus, but the variants foetus and fœtus persist in other English-speaking countries and in some medical contexts, as well as in some other languages (e.g., French). The Oxford English Dictionary print set The Oxford English Dictionary (OED) is a dictionary published by the Oxford University Press (OUP), and is the most successful dictionary of the English language, (not to be confused with the one-volume Oxford Dictionary of English, formerly New Oxford Dictionary of English, of... It has been suggested that Isidro be merged into this article or section. ...


Human fetus

Selection from "Views of a Fetus in the Womb", a drawing by Leonardo da Vinci.
Selection from "Views of a Fetus in the Womb", a drawing by Leonardo da Vinci.

The fetal stage starts at the beginning of the 9th week following fertilization, after the blastocyst, zygote, and embryonic stages. The risk of miscarriage decreases sharply at the beginning of the fetal stage.[7] The fetus is not as sensitive to damage from environmental exposures as the embryo was, though toxic exposures can often cause physiological abnormalities or minor congenital malformation.[citation needed] Fetal growth can be terminated by various factors, including miscarriage, feticide committed by a third party, or induced abortion. Image File history File links Views_of_a_Foetus_in_the_Womb_detail. ... Image File history File links Views_of_a_Foetus_in_the_Womb_detail. ... “Da Vinci” redirects here. ... Categories: Biology stubs ... The blastocyst is an early stage of the human (or any other mammal) development early in pregnancy. ... It has been suggested that Biparental zygote be merged into this article or section. ... For other uses, see Embryo (disambiguation). ... Miscarriage or spontaneous abortion is the natural or spontaneous end of a pregnancy at a stage where the embryo or the fetus is incapable of surviving, generally defined in humans at a gestation of prior to 20 weeks. ... Abortion, in its most common usage, refers to the voluntary or induced termination of pregnancy, generally through the use of surgical procedures or drugs. ...

Development

The following chronology describes some of the specific changes in fetal anatomy and physiology by fertilization age (i.e. the time elapsed since fertilization). Obstetricians often use "gestational age" which, by convention, is measured from 2 weeks earlier than fertilization. For purposes of this article, age is measured from fertilization rather than from two weeks earlier, except as noted. Human heart and lungs, from an older edition of Grays Anatomy. ... This article or section does not cite any references or sources. ... Gestational age is age of a fetus (or newborn infant) from presumed conception. ...


Condition at start of fetal stage

Artist's depiction of fetus 8 weeks after fertilization. The crown-rump length is 1.25 inches.
Artist's depiction of fetus 8 weeks after fertilization. The crown-rump length is 1.25 inches.[8]

The fetal stage commences at the beginning of the 9th week after fertilization (i.e. at the beginning of the 11th week of gestational age).[3] At the start of the fetal stage, the fetus is typically about 30 mm (1.2 inches) in length from crown to rump, and weighs about 8 grams.[3] The head makes up nearly half of the fetus' size.[9] Breathing-like movement of the fetus is necessary for stimulation of lung development, rather than for obtaining oxygen.[10] The heart is beating.[11] Gestational age is age of a fetus (or newborn infant) from presumed conception. ...


The heart, hands, feet, brain and other organs are present, but are not developed sufficiently for the fetus to survive on its own.[12] The fetus is surrounded by amniotic fluid which offers protection and allows room for movement. The pregnant woman's placenta and umbilical cord provide oxygen, nutrients, and allow waste elimination.[12] The amniotic sac is a tough but thin transparent pair of membranes which holds a developing embryo (and later fetus) until shortly before birth. ... The placenta (Latin for cake, referencing its appearance in humans) is an ephemeral organ present in placental vertebrates, such as eutherial mammals and sharks during gestation (pregnancy). ... In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to the placenta. ...


According to current data, fetuses are not capable of feeling pain at the beginning of the fetal stage.[13][14] At this point, complex and generalized movements occur.[15]


9th to 15th weeks

From weeks 9 to 12, the fetal eyelids close and remain closed for several months, and the appearance of the genitals in males and females becomes more apparent.[16] Tooth buds appear, the limbs are long and thin, and red blood cells are produced in the liver, however the majority of red blood cells will be made later in gestation (at 21 weeks) by bone marrow.[17] A fine hair called lanugo develops on the head. The gastrointestinal tract, still forming, starts to collect sloughed skin and lanugo, as well as hepatic products, forming meconium (stool).[18] Fetal skin is almost transparent. The first measurable signs of EEG movement occur in the 12th week.[19] By the end of this stage, the fetus has reached about 15 cm (6 inches). Teeth redirects here. ... A limb (from the Old English lim) is a jointed, or prehensile (as octopus tentacles or new world monkey tails), appendage of the human or animal body; a large or main branch of a tree; a representative, branch or member of a group or organization. ... “Red cell” redirects here. ... For the bird, see Liver bird. ... Lanugo are hairs that grow on the body to attempt to insulate it because of lack of fat. ... Meconium from 12-hour-old newborn — the babys third bowel movement. ... For other uses, see Skin (disambiguation). ... “EEG” redirects here. ...


16th to 25th weeks

Artist's depiction of fetus at 18 weeks after fertilization, about 6.5 inches crown to rump.
Artist's depiction of fetus at 18 weeks after fertilization, about 6.5 inches crown to rump.

The lanugo covers the entire body. Eyebrows, eyelashes, fingernails, and toenails appear. The fetus has increased muscle development. Alveoli (air sacs) are forming in lungs. The nervous system develops enough to control some body functions. The cochlea are now developed, though the myelin sheaths in the neural portion of the auditory system will continue to develop until 18 months after birth. The respiratory system has developed to the point where gas exchange is possible. A woman pregnant for the first time (i.e. a primiparous woman) typically feels fetal movements at about 18-19 weeks, whereas a woman who has already given birth at least two times (i.e. a multiparous woman) will typically feel movements around 16 weeks.[20] By the end of the fifth month, the fetus is about 20 cm (8 inches). Lanugo are hairs that grow on the body to attempt to insulate it because of lack of fat. ... The alveoli (singular:alveolus), tiny hollow sacs which are continuous with the airways, are the sites of gas exchange with the blood. ... The nervous system is a highly specialized network whose principal components are cells called neurons. ... The cochlea is the auditory portion of the inner ear. ... Myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons. ...

26th to 38th weeks

Artist's depiction of fetus at 38 weeks after fertilization, about 20 inches head to toe.
Artist's depiction of fetus at 38 weeks after fertilization, about 20 inches 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 lanugo begins 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 38th week. The fetus is considered full-term between weeks 35 and 40,[21] which means that the fetus is considered sufficiently developed for life outside the uterus.[22] It may be 48 to 53 cm (19 to 21 inches) in length, when born. The thalamus (from Greek θάλαμος = bedroom, chamber, IPA= /ˈθælÉ™mÉ™s/) is a pair and symmetric part of the brain. ... General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... For other uses, see Calcium (disambiguation). ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... Thelarche is the first stage of secondary (postnatal) breast development, usually occurring at the beginning of puberty in girls. ...

Variation in growth

See also: Birth weight

There is much variation in the growth of the fetus. When fetal size is less than expected, that condition is known as intrauterine growth restriction (IUGR) also called fetal growth restriction (FGR); factors affecting fetal growth can be maternal, placental, or fetal.[23] Baby weighed as AGA Birth weight is the weight of a baby at its birth. ... The placenta (Latin for cake, referencing its appearance in humans) is an ephemeral organ present in placental vertebrates, such as eutherial mammals and sharks during gestation (pregnancy). ...


Maternal factors include maternal weight, body mass index, nutritional state, emotional stress, toxin exposure (including tobacco, alcohol, heroin, and other drugs which can also harm the fetus in other ways), and uterine blood flow. For other uses, see Weight (disambiguation). ... A graph of body mass index is shown above. ... In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... Shredded tobacco leaf for pipe smoking Tobacco can also be pressed into plugs and sliced into flakes Tobacco is an agricultural product processed from the fresh leaves of plants in the genus Nicotiana. ... This article does not cite any references or sources. ... For other uses, see Heroin (disambiguation). ...


Placental factors include size, microstructure (densities and architecture), umbilical blood flow, transporters and binding proteins, nutrient utilization and nutrient production.


Fetal factors include the fetus genome, nutrient production, and hormone output. Also, female fetuses tend to weigh less than males, at full term.[23] For other uses, see Hormone (disambiguation). ...


Fetal growth is often classified as follows: small for gestational age (SGA), appropriate for gestational age (AGA), and large for gestational age (LGA).[24] SGA can result in low birth weight, although premature birth can also result in low birth weight. Low birth weight increases risk for perinatal mortality (death shortly after birth), asphyxia, hypothermia, polycythemia, hypocalcemia, immune dysfunction, neurologic abnormalities, and other long-term health problems. SGA may be associated with growth delay, or it may instead be associated with absolute stunting of growth. For other uses, see Death (disambiguation), Dead (disambiguation), or Death (band). ... Suffocation redirects here, for the band, see Suffocation (band). ... Hypothermia is a condition in which an organisms temperature drops below that Required fOr normal metabolism and Bodily functionS. In warm-blooded animals, core [[body Temperature]] is maintained nEar a constant leVel through biologic [[homEostasis]]. But wheN the body iS exposed to cold Its internal mechanismS may be unable... Polycythemia is a condition in which there is a net increase in the total number of red blood cells in the body. ... In medicine, hypocalcaemia is the presence of less than a total calcium of 2. ... Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ... Neurology is the branch of medicine that deals with the nervous system and disorders affecting it. ...

3D ultrasound of 3-inch fetus (about 12 weeks after fertilization)
3D ultrasound of 3-inch fetus (about 12 weeks after fertilization)
3D ultrasound at 17 weeks
3D ultrasound at 17 weeks
3D ultrasound at 20 weeks
3D ultrasound at 20 weeks

Viability

The lower limit of viability is approximately five months gestational age, and usually later.[25] According to The Developing Human: Viability can mean: In an environmental conservation context, viability indicates the ability of a conservation target to persist for many generations or over long time periods. ... Gestational age is age of a fetus (or newborn infant) from presumed conception. ...

Viability is defined as the ability of fetuses to survive in the extrauterine environment... There is no sharp limit of development, age, or weight at which a fetus automatically becomes viable or beyond which survival is assured, but experience has shown that it is rare for a baby to survive whose weight is less than 500 gm or whose fertilization age is less than 22 weeks. Even fetuses born between 26 and 28 weeks have difficulty surviving, mainly because the respiratory system and the central nervous system are not completely differentiated... If given expert postnatal care, some fetuses weighing less than 500 gm may survive; they are referred to as extremely low birth weight or immature infants.... Prematurity is one of the most common causes of morbidity and prenatal death.[26]

During the past several decades, neonatal care has improved with advances in medical science, and therefore the point of viability may have moved earlier.[27] As of 2006, the two youngest children to survive premature birth are thought to be James Elgin Gill (born on 20 May 1987 in Ottawa, Canada, at 21 weeks and 5 days gestational age),[28][29] and Amillia Taylor (born on 24 October 2006 in Miami, Florida, at 21 weeks and 6 days gestational age).[30][31][32] Both children were born just under 20 weeks from fertilization, or a few days past the midpoint of an average full-term pregnancy. Despite their premature births, both developed into healthy children. In most systems of human pregnancy, the condition, premature birth (also known as a preterm birth), occurs when the baby is born within sooner than 36 weeks of completed gestation. ... is the 140th day of the year (141st in leap years) in the Gregorian calendar. ... Year 1987 (MCMLXXXVII) was a common year starting on Thursday (link displays 1987 Gregorian calendar). ... This article is about the capital city of Canada. ... is the 297th day of the year (298th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... This article is about the city in Florida. ... This article is about the U.S. State of Florida. ...


Fetal pain

Main article: Fetal pain

Fetal pain, its existence, and its implications are debated politically and academically. According to the conclusions of a review published in 2005, "Evidence regarding the capacity for fetal pain is limited but indicates that fetal perception of pain is unlikely before the third trimester."[13][33] However, there may be an emerging consensus among developmental neurobiologists that the establishment of thalamocortical connections" (at about 26 weeks) is a critical event with regard to fetal perception of pain.[34] Nevertheless, because pain can involve sensory, emotional and cognitive factors, it is "impossible to know" when painful experiences may become possible, even if it is known when thalamocortical connections are established.[34] The issue of when a fetus can feel pain is a highly divisive and keenly debated one when considering the experience of a fetus during abortion. ... Neurobiology is the study of cells of the nervous system and the organization of these cells into functional circuits that process information and mediate behavior. ... For the computer game developer, see Thalamus Ltd. ...


Whether a fetus has the ability to feel pain and to suffer is part of the abortion debate.[35] [36] For example, legislation has been proposed by pro-life advocates requiring abortion providers to tell a woman that the fetus may feel pain during the abortion procedure, and that require her to accept or decline anesthesia for the fetus.[37] Pain redirects here. ... Suffering, or pain in this sense,[1] is a basic affective experience of unpleasantness and aversion associated with harm or threat of harm in an individual. ... This article is about the social movement. ...


Fetal movement

Main article: Fetal movement

The parts of the fetal brain that control movement will not fully form until late in the second trimester, and the first part of the third trimester.[38] Control of movement is limited at birth, and purposeful voluntary movements start to develop in the first year after bith.[39][40] The human fetus moves throughout its entire development. ...


Locomotor activity begins during the late logical stage, and changes in nature throughout development. Muscles begin to move as soon as they are innervated. These first movements are not reflexive, but arise from nerve impulses originating in the spinal cord. As the nervous system matures, muscles can move in response to stimuli, though this is not a voluntary movement.[41] For other uses, see Embryo (disambiguation). ... This article is about prenatal development in humans. ... For other uses, see Nerve (disambiguation). ... The Spinal cord nested in the vertebral column. ... The nervous system is a highly specialized network whose principal components are cells called neurons. ...


Quickening is the first maternally discernable fetal movement, which is often felt around the middle of pregnancy. 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.[42] Quickening may refer to: Quickening, the transfer of an immortals life force in the Highlander universe. ...


Complex and generalized movements occur at the beginning of the fetal stage, with movements and startles that involve the whole body. These movements occur as muscles and neural pathways begin to develop[15] Movement of hands, hips and knees have been observed at nine weeks,[43] stretches and yawns at ten weeks,[44] and isolated limb movements beginning shortly thereafter.[15]


Circulatory system

Diagram of the human fetal circulatory system.
Diagram of the human fetal circulatory system.

The circulatory system of a human fetus works differently from that of born humans, mainly because the lungs are not in use: the fetus obtains oxygen and nutrients from the mother through the placenta and the umbilical cord.[45] Image File history File links Size of this preview: 372 × 600 pixel Image in higher resolution (558 × 900 pixel, file size: 68 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Fetus ... Image File history File links Size of this preview: 372 × 600 pixel Image in higher resolution (558 × 900 pixel, file size: 68 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Fetus ... For transport in plants, see Vascular tissue. ... For transport in plants, see Vascular tissue. ... This article is about the chemical element and its most stable form, or dioxygen. ... The placenta (Latin for cake, referencing its appearance in humans) is an ephemeral organ present in placental vertebrates, such as eutherial mammals and sharks during gestation (pregnancy). ... In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to the placenta. ...


Blood from the placenta is carried to the fetus by the umbilical vein. About half of this enters the fetal ductus venosus and is carried to the inferior vena cava, while the other half enters the liver proper from the inferior border of the liver. The branch of the umbilical vein that supplies the right lobe of the liver first joins with the portal vein. The blood then moves to the right atrium of the heart. In the fetus, there is an opening between the right and left atrium (the foramen ovale), and most of the blood flows from the right into the left atrium, thus bypassing pulmonary circulation. The majority of blood flow is into the left ventricle from where it is pumped through the aorta into the body. Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries, and re-enters the placenta, where carbon dioxide and other waste products from the fetus are taken up and enter the woman's circulation.[45] Fetal circulation; the umbilical vein is the large, red vessel at the far left The umbilical vein is a blood vessel present during fetal development that carries oxygenated blood from the placenta to the growing fetus. ... In the fetus, the ductus venosus connects the left umbilical vein with the upper inferior vena cava. ... This article may be too technical for most readers to understand. ... For the bird, see Liver bird. ... The portal vein is a major vein in the human body draining blood from the digestive system and its associated glands. ... The heart and lungs, from an older edition of Grays Anatomy. ... In the fetal heart, the foramen ovale allows blood to enter the left atrium from the right atrium. ... Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. ... The aorta (generally pronounced [eɪˈɔːtə] or ay-orta) is the largest artery in the human body, originating from the left ventricle of the heart and bringing oxygenated blood to all parts of the body in the systemic circulation. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...


Some of the blood from the right atrium does not enter the left atrium, but enters the right ventricle and is pumped into the pulmonary artery. In the fetus, there is a special connection between the pulmonary artery and the aorta, called the ductus arteriosus, which directs most of this blood away from the lungs (which aren't being used for respiration at this point as the fetus is suspended in amniotic fluid).[45] The pulmonary arteries carry blood from the heart to the lungs. ... In the developing fetus, the ductus arteriosus (DA) is a shunt connecting the pulmonary artery to the aortic arch that allows much of the blood from the right ventricle to bypass the fetus fluid-filled lungs. ... The amniotic sac is a tough but thin transparent pair of membranes which holds a developing embryo (and later fetus) until shortly before birth. ...


Postnatal development

With the first breath after birth, the system changes suddenly. The pulmonary resistance is dramatically reduced ("pulmo" is from the Latin for "lung"). More blood moves from the right atrium to the right ventricle and into the pulmonary arteries, and less flows through the foramen ovale to the left atrium. The blood from the lungs travels through the pulmonary veins to the left atrium, increasing the pressure there. The decreased right atrial pressure and the increased left atrial pressure pushes the septum primum against the septum secundum, closing the foramen ovale, which now becomes the fossa ovalis. This completes the separation of the circulatory system into two halves, the left and the right. At the end of pregnancy, the fetus must take the journey of childbirth to leave the reproductive female mother. ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... In the fetal heart, the foramen ovale allows blood to enter the left atrium from the right atrium. ...


The ductus arteriosus normally closes off within one or two days of birth, leaving behind the ligamentum arteriosum. The umbilical vein and the ductus venosus closes off within two to five days after birth, leaving behind the ligamentum teres and the ligamentum venosus of the liver respectively. For the ligament of the hip, see Ligamentum teres femoris. ... The ligamentum venosum is the fibrous remnant of the ductus venosus of the fetal circulation. ...


Differences from the adult circulatory system

Remnants of the fetal circulation can be found in adults:[46][47]

Fetal Adult
foramen ovale fossa ovalis
ductus arteriosus ligamentum arteriosum
extra-hepatic portion of the fetal left umbilical vein ligamentum teres hepatis (the "round ligament of the liver").
intra-hepatic portion of the fetal left umbilical vein (the ductus venosus) ligamentum venosum
proximal portions of the fetal left and right umbilical arteries umbilical branches of the internal iliac arteries
distal portions of the fetal left and right umbilical arteries medial umbilical ligaments (urachus)

In addition to differences in circulation, the developing fetus also employs a different type of oxygen transport molecule than adults (adults use adult hemoglobin). Fetal hemoglobin enhances the fetus' ability to draw oxygen from the placenta. Its association curve to oxygen is shifted to the left, meaning that it will take up oxygen at a lower concentration than adult hemoglobin will. This enables fetal hemoglobin to absorb oxygen from adult hemoglobin in the placenta, which has a lower pressure of oxygen than at the lungs. For the adult insect stage, see Imago. ... Two structures in the human body are called foramen ovale, meaning circular hole. ... For the structure in the thigh, see Fossa ovalis (thigh). ... In the developing fetus, the ductus arteriosus (DA) is a shunt connecting the pulmonary artery to the aortic arch that allows much of the blood from the right ventricle to bypass the fetus fluid-filled lungs. ... The ligamentum arteriosum is a small ligament between the pulmonary artery and aortic trunk. ... The liver is an organ in vertebrates including humans. ... Fetal circulation; the umbilical vein is the large, red vessel at the far left The umbilical vein is a blood vessel present during fetal development that carries oxygenated blood from the placenta to the growing fetus. ... For other structures with similar name, see round ligament. ... In the fetus, the ductus venosus connects the left umbilical vein with the upper inferior vena cava. ... The ligamentum venosum is the fibrous remnant of the ductus venosus of the fetal circulation. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... The umbilical artery is a paired artery (with one for each half of the body) that is found in the abdominal and pelvic regions. ... The umbilical artery is a paired artery (with one for each half of the body) that is found in the abdominal and pelvic regions. ... The internal iliac artery (formerly known as the hypogastric artery) is the main artery of the pelvis. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... The medial umbilical ligament is a paired structure found in human anatomy. ... The vesico-urethral portion of the urogenital sinus absorbs the ends of the Wolffian ducts and the associated ends of the renal diverticula, and these give rise to the trigone of the bladder and part of the prostatic urethra. ... A transport protein is a protein involved in facilitated diffusion. ... Structure of hemoglobin. ... Fetal hemoglobin protein structure Fetal hemoglobin (also hemoglobin F or HbF) is the main oxygen transport protein in the fetus during the last seven months of development in the womb. ...


Developmental problems

See also: Congenital disorder

Congenital anomalies are anomalies that are acquired before birth. Infants with certain congenital anomalies of the heart can survive only as long as the ductus remains open: in such cases the closure of the ductus can be delayed by the administration of prostaglandins to permit sufficient time for the surgical correction of the anomalies. Conversely, in cases of patent ductus arteriosus, where the ductus does not properly close, drugs that inhibit prostaglandin synthesis can be used to encourage its closure, so that surgery can be avoided. A congenital disorder is any medical condition that is present at birth. ... E1 - Alprostadil I2 - Prostacyclin A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. ... Patent ductus arteriosus (PDA) is a congenital heart defect wherein a childs ductus arteriosus fails to close after birth. ...


A developing fetus is highly susceptible to anomalies in its growth and metabolism, increasing the risk of birth defects. One area of concern is the pregnant woman's lifestyle choices made during pregnancy [48] Diet is especially important in the early stages of development. Studies show that supplementation of the woman's diet with folic acid reduces the risk of spina bifida and other neural tube defects. Another dietary concern is whether the woman eats breakfast. Skipping breakfast could lead to extended periods of lower than normal nutrients in the woman's blood, leading to a higher risk of prematurity, or other birth defects in the fetus. During this time alcohol consumption may increase the risk of the development of Fetal alcohol syndrome, a condition leading to mental retardation in some infants.[49] Smoking during pregnancy may also lead to reduced birth weight. Low birth weight is defined as 2500 grams (5.5 lb). Low birth weight is a concern for medical providers due to the tendency of these infants, described as premature by weight, to have a higher risk of secondary medical problems. Folic acid and folate (the anion form) are forms of the water-soluble Vitamin B9. ... In the developing vertebrate nervous system, the neural tube is the precursor of the central nervous system, which comprises the brain and spinal cord. ... Prematurity is the condition of being born before a full gestation. ... Fetal alcohol syndrome or FAS is a disorder of permanent birth defects that occurs in the offspring of women who drink alcohol during pregnancy. ... Mental retardation is a term for a pattern of persistently slow learning of basic motor and language skills (milestones) during childhood, and a significantly below-normal global intellectual capacity as an adult. ...


Legal issues

Main articles: Abortion Debate and Fetal rights

In the United States, some states have laws that impose strict punishments for those who inflict violence that results in damage to a fetus or the unwanted termination of a pregnancy. The severity of the punishment, and the stage of fetal development where laws start to apply vary from state to state.[50] Issues of discussion The abortion debate refers to discussion and controversy surrounding the moral and legal status of abortion. ... The term fetal rights can refer either to legal rights accorded to fetuses or to the moral rights that some people ascribe to them. ...


Abortion of a fetus is legal in many countries such as Australia, Canada, Mexico, UK and USA. International status of abortion law  Legal on request  Legal for rape, maternal life, health, mental health, socioecomic factors, and/or fetal defects  Legal for or illegal with exception for rape, maternal life, health, fetal defects, and/or mental health  Illegal with exception for rape, maternal life, health, and/or mental...


Non-human fetuses

Histological slice of a rat fetus at E17 from BrainMaps.org

The fetus of most mammals develops similarly to the Homo sapiens fetus. After the first stages of development, the human embryo reaches a stage very similar to all other vertebrates.[51] The anatomy of the area surrounding a fetus is different in litter-bearing animals compared to humans: each fetus is surrounded by placental tissue and is lodged along one of two long uteri instead of the single uterus found in a human female. Development at birth is similar, with animals also having a poorly developed sense of vision and other senses.[citation needed]
Image File history File links This is a lossless scalable vector image. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A thin section of lung tissue stained with hematoxylin and eosin. ... Homo sapiens (Latin: wise man) is the scientific name for the human species. ... Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ...


See also

Wikimedia Commons has media related to:

Image File history File links Commons-logo. ... For other uses, see Embryo (disambiguation). ... This article is about human pregnancy in biological females. ... For other uses, see Child (disambiguation). ... Superfetation (also spelt superfoetation, based on a false etymology — see fetus) is the formation of a fetus while another fetus is already present in the uterus. ... The study of neural development draws on both neuroscience and developmental biology to describe the cellular and molecular mechanisms by which complex nervous systems emerge during embryonic development and throughout life. ... Fetoscopy is an endoscopic procedure during pregnancy to allow access to the fetus, the amniotic cavity, the umbilical cord, and the fetal side of the placenta. ... Fetal position(also spelt FOETAL) is a medical term used to describe the positioning of the body of a prenatal fetus as it develops. ...

References

  1. ^ MedicineNet.com: "The unborn offspring from the end of the 8th week after conception (when the major structures have formed) until birth." See also The Columbia Encyclopedia (Sixth Edition). Retrieved 2007-03-05: "the fetal stage begins seven to eight weeks after fertilization of the egg, when the embryo assumes the basic shape of the newborn and all the organs are present."
  2. ^ Some authorities suggest that the embryonic stage may last only seven weeks. See Encyclopedia Britannica: "In humans, the organism is called an embryo for the first seven or eight weeks after conception, after which it is called a fetus." Also see The Columbia Encyclopedia (Sixth Edition). Retrieved 2007-03-05: "the fetal stage begins seven to eight weeks after fertilization of the egg, when the embryo assumes the basic shape of the newborn and all the organs are present."
  3. ^ a b c Klossner, N. Jayne Introductory Maternity Nursing (2005): "The fetal stage is from the beginning of the 9th week after fertilization and continues until birth"
  4. ^ Harper, Douglas. (2001). Online Etymology Dictionary. Retrieved 2007-01-20.
  5. ^ The American Heritage Dictionary of the English Language, Fourth Edition. Retrieved 2007-01-22.
  6. ^ Aronson, Jeff (July 1997). "When I use a word...:Oe no!". British Medical Journal 315 (1). BMJ Publishing Group Ltd. Retrieved on 2006-06-29.
  7. ^Q&A: Miscarriage. (August 6 , 2002). BBC News. Retrieved 2007-04-22: “The risk of miscarriage lessens as the pregnancy progresses. It decreases dramatically after the 8th week.”
    Lennart Nilsson, A Child is Born 91 (1990): at eight weeks, "the danger of a miscarriage … diminishes sharply."
    • “Women’s Health Information”, Hearthstone Communications Limited: “The risk of miscarriage decreases dramatically after the 8th week as the weeks go by.” Retrieved 2007-04-22.
  8. ^ Marc H. Bornstein, Michael E. Lamb. Developmental Science: An Advanced Textbook, page 227 (2005): "At 8 weeks, fetuses measure 3.18 cm from crown to rump (1.25 inches)."
  9. ^ MedlinePlus
  10. ^ Institute of Medicine of the National Academies, Preterm Birth: Causes, Consequences, and Prevention (2006), page 317. Retrieved 2008-03-12: "Fetal breathing movements begin as early as 10 weeks of gestation, and the breathing of amniotic fluid in and out is essential for the stimulation of lung development."
  11. ^ Greenfield, Marjorie. “Dr. Spock.com". Retrieved 2007-01-20.
  12. ^ a b The Columbia Encyclopedia (Sixth Edition). Retrieved 2007-03-05.
  13. ^ a b Lee, Susan (August 24/31, 2005). "Fetal Pain A Systematic Multidisciplinary Review of the Evidence". The Journal of the American Medical Association 294 (8). the American Medical Association. Retrieved on 2008-02-14. (see Fetal Pain section) Two authors of the study published in JAMA did not report their abortion-related activities, which pro-life groups called a conflict of interest; the editor of JAMA responded that JAMA probably would have mentioned those activities if they had been disclosed, but still would have published the study. See Denise Grady, “Study Authors Didn't Report Abortion Ties”, New York Times (2005-08-26).
  14. ^ "Study: Fetus feels no pain until third trimester" MSNBC
  15. ^ a b c Prechtl, Heinz"Prenatal and Early Postnatal Development of Human Motor Behavior" in Handbook of brain and behaviour in human development, Kalverboer and Gramsbergen eds., pp. 415-418 (2001 Kluwer Academic Publishers): "The first movements to occur are sideward bendings of the head....At 9-10 weeks postmestrual age complex and generalized movements occur. These are the so-called general movements (Prechtl et al., 1979) and the startles. Both include the whole body, but the general movements are slower and have a complex sequence of involved body parts, while the startle is a quick, phasic movement of all limbs and trunk and neck."
  16. ^ Medline Plus Medical Encyclopedia
  17. ^ MedlinePlus
  18. ^ MedlinePlus
  19. ^ Vogel, Friedrich. Genetics and the Electroencephalogram (Springer 2000): "Slow EEG activity (0.5 – 2 c/s) can be demonstrated in the fetus even at the conceptual age of three months." Retrieved 2007-03-05.
  20. ^ Levene, Malcolm et al. Essentials of Neonatal Medicine (Blackwell 2000), page 8. Retrieved 2007-03-04.
  21. ^ Your Pregnancy: 36 Weeks BabyCenter.com Retrieved June 1, 2007.
  22. ^ Word Web Online, retrieved 2007-01-26.
  23. ^ a b Holden, Chris and MacDonald, Anita. Nutrition and Child Health (Elsevier 2000). Retrieved 2007-03-04.
  24. ^ Queenan, John. Management of High-Risk Pregnancy (Blackwell 1999). Retrieved 2007-03-04.
  25. ^ Halamek, Louis. "Prenatal Consultation at the Limits of Viability", NeoReviews, Vol.4 No.6 (2003): "most neonatologists would agree that survival of infants younger than approximately 22 to 23 weeks’ estimated gestational age [i.e. 20 to 21 weeks' estimated fertilization age] is universally dismal and that resuscitative efforts should not be undertaken when a neonate is born at this point in pregnancy."
  26. ^ Moore, Keith and Persaud, T. (2003). The Developing Human: Clinically Oriented Embryology'. Philadelphia: Saunders, p. 103. ISBN 0-7216-9412-8. 
  27. ^ Roe v. Wade, 410 U.S. 113 (1973) ("viability is usually placed at about seven months (28 weeks) but may occur earlier, even at 24 weeks.") Retrieved 2007-03-04.
  28. ^ Powell's Books - Guinness World Records 2004 (Guinness Book of Records) by. Retrieved on 2007-11-28.
  29. ^ Miracle child. Retrieved on 2007-11-28.
  30. ^ trithuc.thanhnienkhcn.org.vn. Retrieved on 2007-11-28.
  31. ^ "Most-premature baby allowed home", BBC News, 2007-02-21. Retrieved on 2007-05-05. 
  32. ^ Baptist Hospital of Miami, Fact Sheet (2006).
  33. ^ "Study: Fetus feels no pain until third trimester" MSNBC
  34. ^ a b Johnson, Martin and Everitt, Barry. Essential reproduction (Blackwell 2000): "The multidimensionality of pain perception, involving sensory, emotional, and cognitive factors may in itself be the basis of conscious, painful experience, but it will remain difficult to attribute this to a fetus at any particular developmental age." Retrieved 2007-02-21.
  35. ^ White, R. Frank. "Are We Overlooking Fetal Pain and Suffering During Abortion?", American Society of Anesthesiologists Newsletter (October 2001). Retrieved 2007-03-10.
  36. ^ David, Barry & and Goldberg, Barth. "Recovering Damages for Fetal Pain and Suffering", Illinois Bar Journal (December 2002). Retrieved 2007-03-10.
  37. ^ Weisman, Jonathan. "House to Consider Abortion Anesthesia Bill", Washington Post 2006-12-05. Retrieved 2007-02-06.
  38. ^ The development of cerebral connections during the first 20–45 weeks’ gestation. Seminars in Fetal and Neonatal Medicine, Volume 11, Issue 6, Pages 415-422
  39. ^ Stanley, Fiona et al. "Cerebral Palsies: Epidemiology and Causal Pathways", page 48 (2000 Cambridge University Press): "Motor competance at birth is limited in the human neonate. The voluntary control of movement develops and matures during a prolonged period up to puberty...."
  40. ^ Becher, Julie-Claire. "Insights into Early Fetal Development", Behind the Medical Headlines (Royal College of Physicians of Edinburgh and Royal College of Physicians and Surgeons of Glasgow October 2004): "Purposive movement depends on brain maturation. This begins at about 18 weeks and progressively replaces reflex movements, which disappear by about 8 months after birth....Reflexes are very different from purposeful voluntary movements which develop during the first year of life."
  41. ^ Vaughan 1996, p. 208.
  42. ^ Van Der Ziel, Cornelia & Tourville, Jacqueline. Big, Beautiful & Pregnant: Expert Advice And Comforting Wisdom for the Expecting Plus-size Woman (Marlowe 2006). Retrieved 2007-02-15.
  43. ^ Valman, H. and Pearson, J. "What the Fetus Feels", British Medical Journal, (January 26, 1980). Retrieved 2007-03-04: "Nine weeks after conception...fingers [bend] round an object in the palm of his hand. In response to a touch on the sole of his foot...hips and knees [bend] to move away from the touching object."
  44. ^ Butterworth, George and Harris, Margaret. Principles of developmental psychology, page 48 (Psychology Press 1994): "stretch and yawn pattern at 10 weeks."
  45. ^ a b c Whitaker, Kent. Comprehensive Perinatal and Pediatric Respiratory Care (Delmar 2001). Retrieved 2007-03-04.
  46. ^ Dudek, Ronald and Fix, James. Board Review Series Embryology (Lippincott 2004). Retrieved 2007-03-04.
  47. ^ University of Michigan Medical School, Fetal Circulation and Changes at Birth. Retrieved 2007-03-04.
  48. ^ Dalby, JT. (1978).Environmental effects on prenatal development Journal of Pediatric Psychology, 3, 105-109.
  49. ^ Streissguth, A. (1997). Fetal Alcohol Syndrome: A Guide for Families and Communities. Baltimore: Brookes Publishing. ISBN 1-55766-283-5.
  50. ^ National Conference of State Legislatures. (June 2006). "Fetal Homicide". Retrieved January 19, 2007.
  51. ^ ZFIN, Pharyngula Period (24-48 h). Modified from: Kimmel et al., 1995. Developmental Dynamics 203:253-310. Downloaded 5 March 2007.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... This article is about the day. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... This article is about the day. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 20th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 22nd day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 180th day of the year (181st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 112th day of the year (113th in leap years) in the Gregorian calendar. ... Lennart Nilsson (b. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 112th day of the year (113th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 71st day of the year (72nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 20th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... This article is about the day. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 45th day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 238th day of the year (239th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... This article is about the day. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 26th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 332nd day of the year (333rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 332nd day of the year (333rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 332nd day of the year (333rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 52nd day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 125th day of the year (126th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 52nd day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 69th day of the year (70th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 69th day of the year (70th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 339th day of the year (340th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 37th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 46th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ...

External links

Preceded by
Embryo
Stages of human development
Fetus
Succeeded by
Infant
The placenta (Latin for cake, referencing its appearance in humans) is an ephemeral organ present in placental vertebrates, such as eutherial mammals and sharks during gestation (pregnancy). ... Decidua is the term for the uterine lining (endometrium) during a pregnancy. ... Before the fertilized ovum reaches the uterus, the mucous membrane of the body of the uterus undergoes important changes and is then known as the decidua. ... Chorionic villi are villi that sprout from the chorion, in order to give a maximum area of contact with the maternal blood. ... The trophoblast proliferates rapidly and forms a network of branching processes which cover the entire ovum and invade and destroy the maternal tissues and open into the maternal bloodvessels, with the result that the spaces in the trophoblastic network are filled with maternal blood; these spaces communicate freely with one... The gestational sac is the only available intrauterine structure that can be used to determine if an intrauterine pregnancy (IUP) exists, until the embryo is identified. ... For the alien race in Stephen Donaldsons The Gap Cycle, see Amnion (Gap Cycle). ... A drawing of the amniotic sac from Grays Anatomy. ... amniotic sac The amniotic sac is a tough but thin transparent pair of membranes, which hold a developing embryo (and later fetus) until shortly before birth. ... For the entertainment company see Chorion (company) The chorion surrounds the embryo and other membranes. ... An Introduction to Histogenesis Histogenesis is defined as the formation of tissues and organs from undifferentiated cells (Encarta Dictionary). ... Programmed cell death (PCD) is the deliberate suicide of an unwanted cell in a multicellular organism. ... Mouse embryonic stem cells. ... The cells that give rise to the gametes are often set aside during cleavage. ... Organogenesis is a stage of animal development where the ectoderm, endoderm, and mesoderm are formed. ... The vertebrate limb arises out of a general morphogenetic area called a limb field. ... In embryology, the limb bud is a structure formed by the developing limb, derived from lateral plate mesoderm[citation needed]. It is intimately related with the apical ectodermal ridge, which secretes factors inducing the initial differentiation of the limb bud. ... The Apical Ectodermal Ridge (AER) is a critical component in vertebrate limb development. ... Transverse section showing the lens and the optic cup. ... Cutaneous structures arise from the epidermis and include a variety of features such as hair, feathers, claws and nails. ... The heart is the first functional organ in a vertebrate embryo. ... In prenatal development, the urinary and reproductive organs are developed from the intermediate mesoderm. ...

  Results from FactBites:
 
fetus - HighBeam Encyclopedia (550 words)
fetus term used to describe the unborn offspring in the uterus of vertebrate animals after the embryonic stage (see embryo).
If the fetus is expelled before 36 weeks of gestation are completed, it often can survive outside the womb, but artificial assistance, such as intravenous feedings and strict maintainance of the ambient temperature, may be needed during the remainder of its normal developmental period.
Genug ist genug: a fetus is not a kidney.
fetus: Definition and Much More from Answers.com (2227 words)
The circulatory system of a human fetus works differently from that of born humans, mainly because the lungs are not in use: the fetus obtains oxygen and nutrients from the woman through the placenta and the umbilical cord.
In the fetus, there is a special connection between the pulmonary artery and the aorta, called the ductus arteriosus, which directs most of this blood away from the lungs (which aren't being used for respiration at this point as the fetus is suspended in amniotic fluid).
The anatomy of the area surrounding a fetus, however, is different in litter-bearing animals compared to humans: each fetus is surrounded by placental tissue and is lodged along one of two long uteri instead of the single uterus found in a human female.
  More results at FactBites »

 
 

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