Fetus

fetalfoetusfetusesfoetalviabilityfœtusfoetuseshuman fetusalien fetusbaby
A fetus or foetus (plural fetuses, feti, foetuses, or foeti) is the unborn offspring of an animal that develops from an embryo.wikipedia
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Embryo

embryosembryonalhuman embryos
A fetus or foetus (plural fetuses, feti, foetuses, or foeti) is the unborn offspring of an animal that develops from an embryo.
A newly developing human is typically referred to as an embryo until the ninth week after conception (see human embryogenesis), when it is then referred to as a fetus.

Intrauterine growth restriction

intrauterine growth retardationfetal growth restrictionIUGR
When fetal size is less than expected, the condition is known as intrauterine growth restriction (IUGR) also called fetal growth restriction (FGR); factors affecting fetal growth can be maternal, placental, or fetal.
The causes can be many, but most often involve poor maternal nutrition or lack of adequate oxygen supply to the fetus.

American and British English spelling differences

spelling differencesorsee spelling differences
A fetus or foetus (plural fetuses, feti, foetuses, or foeti) is the unborn offspring of an animal that develops from an embryo.
Examples (with non-American letter in bold): aeon, anaemia, anaesthesia, caecum, caesium, coeliac, diarrhoea, encyclopaedia, faeces, foetal, gynaecology, haemoglobin, haemophilia, leukaemia, oesophagus, oestrogen, orthopaedic, palaeontology, paediatric, paedophile.

Environmental toxicants and fetal development

environmental toxins in pregnancyEnvironmental toxins and fetal developmentenvironmental toxin in 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.
Environmental toxicants and fetal development is the impact of different toxic substances from the environment on the development of the fetus.

Crown-rump length

crown to rump lengthcrown-rump
At the start of the fetal stage, the fetus is typically about 30 mm in length from crown-rump, and weighs about 8 grams.
Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump).

Lung

lungspulmonaryright lung
Breathing-like movements of the fetus are necessary for the stimulation of lung development, rather than for obtaining oxygen.
When the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe.

Gestational age

gestationgestationalweeks of gestation
In human prenatal development, fetal development begins from the ninth week after fertilisation (or eleventh week gestational age) and continues until birth.

Umbilical cord

umbilicalcord[umbilical] cord
Placental factors include size, microstructure (densities and architecture), umbilical blood flow, transporters and binding proteins, nutrient utilization and nutrient production.
In placental mammals, the umbilical cord (also called the navel string, birth cord or funiculus umbilicalis) is a conduit between the developing embryo or fetus and the placenta.

Uterus

wombuterineuteri
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.
It is within the uterus that the fetus develops during gestation.

Fetal viability

viabilityviableviability of the fetus
Fetal viability refers to a point in fetal development at which the fetus may survive outside the womb.
Fetal viability or foetal viability is the ability of a fetus to survive outside the uterus.

Infant

neonatalinfancynewborn
When such premature babies are born, the main causes of mortality are that the respiratory system and the central nervous system are not completely differentiated.
In medical contexts, newborn or neonate (from Latin, neonatus, newborn) refers to an infant in the first 28 days after birth; the term applies to premature, full term, and postmature infants; before birth, the term "fetus" is used.

Human embryonic development

human embryoembryogenesishuman embryogenesis
The heart and blood vessels of the circulatory system, form relatively early during embryonic development, but continue to grow and develop in complexity in the growing fetus.
Embryonic development in the human, covers the first eight weeks of development; at the beginning of the ninth week the embryo is termed a fetus.

Anatomy

anatomistanatomicalanatomically
However, a fetus is characterized by the presence of all the major body organs, though they will not yet be fully developed and functional and some not yet situated in their final anatomical location.
Most other mammals have a placenta through which the developing foetus obtains nourishment, but in marsupials, the foetal stage is very short and the immature young is born and finds its way to its mother's pouch where it latches on to a nipple and completes its development.

Ductus venosus

Patent ductus venosus
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.
In the fetus, the ductus venosus (Arantius' duct after Julius Caesar Aranzi ) shunts a portion of umbilical vein blood flow directly to the inferior vena cava.

Lanugo

lanugo haira common symptombaby hair
The lanugo, or fine hair, begins to disappear, until it is gone except on the upper arms and shoulders.
During human development, the lanugo grows on fetuses as a normal part of gestation, but it is usually shed and replaced by vellus hair at about thirty-three to thirty-six weeks of gestational age.

Blood

human bloodhematologicaloxygen consumption
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.
A fetus, receiving oxygen via the placenta, is exposed to much lower oxygen pressures (about 21% of the level found in an adult's lungs), so fetuses produce another form of hemoglobin with a much higher affinity for oxygen (hemoglobin F) to function under these conditions.

Ductus arteriosus

ductus arteriosisductal
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 ductus arteriosus, also called the ductus Botalli, is a blood vessel in the developing fetus connecting the trunk of the pulmonary artery to the proximal descending aorta.

Umbilical vein

umbilicalumbilical veins[umbilical] veins
Blood from the placenta is carried to the fetus by the umbilical vein.
The umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta into the growing fetus.

Heart

cardiachuman heartapex of the heart
The heart and blood vessels of the circulatory system, form relatively early during embryonic development, but continue to grow and develop in complexity in the growing fetus.
After 9 weeks (start of the fetal stage) it starts to decelerate, slowing to around 145 (±25) bpm at birth.

Passive immunity

maternal antibodiespassive immunizationimmunization, passive
Maternal IgG antibodies cross the placenta, giving the fetus passive immunity against those diseases for which the mother has antibodies.
Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin (obtained from humans, horses, or other animals) are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy.

Vertically transmitted infection

vertical transmissionmother-to-child transmissionvertically
When this is insufficient, mother-to-child transmission of infectious diseases can occur.
A vertically transmitted infection is an infection caused by pathogens (such as bacteria and viruses) that use mother-to-child transmission, that is, transmission directly from the mother to an embryo, fetus, or baby during pregnancy or childbirth.

Circulatory system

cardiovascularcirculationcardiovascular system
The heart and blood vessels of the circulatory system, form relatively early during embryonic development, but continue to grow and develop in complexity in the growing fetus.
Before birth the fetus obtains oxygen (and nutrients) from the mother through the placenta and the umbilical cord.

Miscarriage

miscarriedspontaneous abortionmiscarriages
Smoking during pregnancy may also lead to miscarriages and low birth weight (2500 grams, 5.5 lb).
Miscarriage, also known as spontaneous abortion and pregnancy loss, is the natural death of an embryo or fetus before it is able to survive independently.

Amniotic fluid

amnioticamniotic fluid cellsamniotic fluid membranes
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 volume of amniotic fluid increases with the growth of fetus.

Liver

hepaticliver protein synthesislivers
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.
In the first trimester fetus, the liver is the main site of red blood cell production.