Amniotic fluid
Encyclopedia
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac
of a pregnant woman.
At first it is mainly water with electrolytes
, but about the 12-14th week the liquid also contains protein
s, carbohydrate
s, lipid
s and phospholipid
s, and urea
, all of which aid in the growth of the fetus.
The volume of amniotic fluid increases with linear regression to the growth of fetus. From the 10th to the 20th week it increases from 25ml to 400ml approximately. From the 8th week, when the fetal kidneys begin to function, fetal urine is also present in the AF. Approximately in the 10th week the breathing and swallowing of the fetus slightly decrease the amount of AF, but neither urination nor swallowing contributes significantly to AF quantity changes, up until the 25 week, when keratinization of skin is complete. Then the linear regression between AF and fetal growth cease to exist. It reaches the plateau of 800ml at the 28 week (gestational age
). The amount of fluid declines to roughly 400 ml at 42 weeks ga.
The forewaters are released when the amnion ruptures
. This is commonly known as the time when a woman's "water breaks". When this occurs during labour
at term
, it is known as "spontaneous rupture of membranes" (SROM). If the rupture precedes labour at term, however, it is referred to as "premature rupture of membranes" (PROM). The majority of the hindwaters remain inside the womb until the baby is born. Artificial rupture of membrane (ARM), a manual rupture of the amniotic sac, can also be performed to release the fluid if the amnion has not spontaneously ruptured.
. As well, amniotic fluid protects the developing baby by cushioning against blows to the mother's abdomen, allows for easier fetal movement, promotes muscular/skeletal development, and helps protect the fetus from heat loss.
Analysis of amniotic fluid, drawn out of the mother's abdomen in an amniocentesis
procedure, can reveal many aspects of the baby's genetic health. This is because the fluid also contains fetal cells, which can be examined for genetic defects.
of Wake Forest University
, a team from Harvard University
, and Italian Paolo de Coppi, have found that amniotic fluid is also a plentiful source of non-embryonic stem cells. These cells have demonstrated the ability to differentiate into a number of different cell-types, including brain, liver and bone.
It is possible to conserve the stem cells extracted from amniotic fluid in private stem cells banks. Some private companies offer this service for a fee.
) can be a cause or an indicator of problems for the mother and baby. The majority of pregnancies proceed normally and the baby is born healthy, but this isn't always the case. Babies with too little amniotic fluid can develop contractures of the limbs, clubbing of the feet and hands, and also develop a life threatening condition called hypoplastic lungs. If a baby is born with hypoplastic lungs, which are small underdeveloped lungs, this condition is potentially fatal and the baby can die shortly after birth.
On every prenatal visit, the obstetrician/gynaecologist or midwife should measure the patient's fundal height
with a tape measure. It is important that the fundal height be measured and properly recorded to ensure proper fetal growth and the increasing development of amniotic fluid. The obstetrician/gynaecologist should also routinely ultrasound
the patient—this procedure will also give an indication of proper fetal growth and amniotic fluid development. Oligohydramnios can be caused by infection, kidney dysfunction or malformation (since much of the late amniotic fluid volume is urine), procedures such as chorionic villus sampling
(CVS), and preterm premature rupture of membranes (PPROM).
Oligohydramnios can sometimes be treated with bed rest
, oral and intravenous hydration, antibiotic
s, steroid
s, and amnioinfusion. It is also important to keep the baby warm.
Amniotic sac
The amniotic sac is the sac in which the fetus develops in amniotes. It is a tough but thin transparent pair of membranes, which hold a developing embryo until shortly before birth. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the Chorion,...
of a pregnant woman.
Development of amniotic fluid
From the very beginning of the formation of the extracoelomal cavity amniotic fluid [AF] can be detected. This firstly water-like fluid originates from the maternal plasma, and passes through the fetal membranes by osmotic and hydrostatic forces. As the placental and fetal vessels develop, the fluid passes through the fetal tissue, as the exsudatum of the skin. After the 20th-25th week of pregnancy when the keratinization of skin occours, the quantity of amniotic fluid begins to depend on the factors that comprise the circulation of AF.At first it is mainly water with electrolytes
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
, but about the 12-14th week the liquid also contains protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s, lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s and phospholipid
Phospholipid
Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from...
s, and urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
, all of which aid in the growth of the fetus.
The volume of amniotic fluid increases with linear regression to the growth of fetus. From the 10th to the 20th week it increases from 25ml to 400ml approximately. From the 8th week, when the fetal kidneys begin to function, fetal urine is also present in the AF. Approximately in the 10th week the breathing and swallowing of the fetus slightly decrease the amount of AF, but neither urination nor swallowing contributes significantly to AF quantity changes, up until the 25 week, when keratinization of skin is complete. Then the linear regression between AF and fetal growth cease to exist. It reaches the plateau of 800ml at the 28 week (gestational age
Gestational age
Gestational age relates to the age of an embryo or fetus . There is some ambiguity in how it is defined:*In embryology, gestational age is the time elapsed since conception. This interval is also termed fertilisation age....
). The amount of fluid declines to roughly 400 ml at 42 weeks ga.
The forewaters are released when the amnion ruptures
Rupture of membranes
Rupture of membranes or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. Normally, or "spontaneously", it occurs at full term at the onset of, or during, labor...
. This is commonly known as the time when a woman's "water breaks". When this occurs during labour
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
at term
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
, it is known as "spontaneous rupture of membranes" (SROM). If the rupture precedes labour at term, however, it is referred to as "premature rupture of membranes" (PROM). The majority of the hindwaters remain inside the womb until the baby is born. Artificial rupture of membrane (ARM), a manual rupture of the amniotic sac, can also be performed to release the fluid if the amnion has not spontaneously ruptured.
Functions of amniotic fluid
Amniotic fluid is "inhaled" and "exhaled" by the fetus. It is essential that fluid be breathed into the lungs in order for them to develop normally. Swallowed amniotic fluid also creates urine and contributes to the formation of meconiumMeconium
Meconium is the earliest stools of an infant. Unlike later feces, meconium is composed of materials ingested during the time the infant spends in the uterus: intestinal epithelial cells, lanugo, mucus, amniotic fluid, bile, and water. Meconium is almost sterile, unlike later feces, is viscous and...
. As well, amniotic fluid protects the developing baby by cushioning against blows to the mother's abdomen, allows for easier fetal movement, promotes muscular/skeletal development, and helps protect the fetus from heat loss.
Analysis of amniotic fluid, drawn out of the mother's abdomen in an amniocentesis
Amniocentesis
Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...
procedure, can reveal many aspects of the baby's genetic health. This is because the fluid also contains fetal cells, which can be examined for genetic defects.
Amniotic fluid and stem cells
Recent studies show that amniotic fluid contains a considerable quantity of stem cells. These amniotic stem cells are multipotent and able to differentiate into various tissues, which may be useful for future human application. Some researchers, including Anthony AtalaAnthony Atala
Anthony Atala, M.D., is the W.H. Boyce Professor and Director of the Wake Forest Institute for Regenerative Medicine, and Chair of the Department of Urology at the Wake Forest University School of Medicine in North Carolina...
of Wake Forest University
Wake Forest University
Wake Forest University is a private, coeducational university in the U.S. state of North Carolina, founded in 1834. The university received its name from its original location in Wake Forest, north of Raleigh, North Carolina, the state capital. The Reynolda Campus, the university's main campus, is...
, a team from Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
, and Italian Paolo de Coppi, have found that amniotic fluid is also a plentiful source of non-embryonic stem cells. These cells have demonstrated the ability to differentiate into a number of different cell-types, including brain, liver and bone.
It is possible to conserve the stem cells extracted from amniotic fluid in private stem cells banks. Some private companies offer this service for a fee.
Complications related to amniotic fluid
Too little amniotic fluid (OligohydramniosOligohydramnios
Oligohydramnios is a condition in pregnancy characterized by a deficiency of amniotic fluid. It is the opposite of polyhydramnios.-Diagnosis:Diagnosis is made by ultrasound measurement of the amniotic fluid index...
) can be a cause or an indicator of problems for the mother and baby. The majority of pregnancies proceed normally and the baby is born healthy, but this isn't always the case. Babies with too little amniotic fluid can develop contractures of the limbs, clubbing of the feet and hands, and also develop a life threatening condition called hypoplastic lungs. If a baby is born with hypoplastic lungs, which are small underdeveloped lungs, this condition is potentially fatal and the baby can die shortly after birth.
On every prenatal visit, the obstetrician/gynaecologist or midwife should measure the patient's fundal height
Fundal height
Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess fetal growth and development. It is measured from the top of the mother's uterus to the top of the mother's pubic bone in centimeters. It should match the fetus' gestational age in weeks within 1 to 3 cm,...
with a tape measure. It is important that the fundal height be measured and properly recorded to ensure proper fetal growth and the increasing development of amniotic fluid. The obstetrician/gynaecologist should also routinely ultrasound
Medical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
the patient—this procedure will also give an indication of proper fetal growth and amniotic fluid development. Oligohydramnios can be caused by infection, kidney dysfunction or malformation (since much of the late amniotic fluid volume is urine), procedures such as chorionic villus sampling
Chorionic villus sampling
Chorionic villus sampling , sometimes misspelled "chorionic villous sampling", is a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus and testing it...
(CVS), and preterm premature rupture of membranes (PPROM).
Oligohydramnios can sometimes be treated with bed rest
Bed rest
Bed rest is a medical treatment involving a period of consistent recumbence in bed. It is used as a treatment for an illness or medical condition, especially when prescribed or chosen rather than resulting from severe prostration or imminent death...
, oral and intravenous hydration, antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s, steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
s, and amnioinfusion. It is also important to keep the baby warm.