Editing Amniotic fluid (section)

== Development==

Amniotic fluid is present from the formation of the [[gestational sac]]. Amniotic fluid is in the [[amniotic sac]]. It is generated from maternal [[blood plasma|plasma]], and passes through the fetal membranes by osmotic and hydrostatic forces. When fetal kidneys begin to function around week 16, fetal urine also contributes to the fluid.<ref name=LARSEN2001 /> In earlier times, it was believed that the amniotic fluid was composed entirely of excreted fetal urine.

The fluid is absorbed through the fetal tissue and skin.<ref name="NatureUnderwood">{{cite journal | title=Amniotic Fluid: Not Just Fetal Urine Anymore - Journal of Perinatology | journal=Journal of Perinatology | date=May 2005 | volume=25 | issue=5 | pages=341–348 | doi=10.1038/sj.jp.7211290 | last1=Underwood | first1=Mark A. | last2=Gilbert | first2=William M. | last3=Sherman | first3=Michael P. | pmid=15861199 | s2cid=1302607 | doi-access=free }}</ref> After 22 to 25 week of pregnancy, [[keratin]]ization of an embryo's skin occurs. When this process completes around the 25th week,<ref name="NatureUnderwood"/> the fluid is primarily absorbed by the fetal gut for the remainder of gestation.<ref name=LARSEN2001>{{cite book|last1=Larsen|first1=William J.|title=Human embryology|date=2001|publisher=Churchill Livingstone|location=Philadelphia, Pa.|isbn=978-0443065835|pages=490|edition=3.}}</ref>

===Contents===
At first, amniotic fluid is mainly water with [[electrolyte]]s, but by about the 12–14th week the liquid also contains [[protein]]s, [[carbohydrate]]s, [[lipid]]s and [[phospholipid]]s, [[urea]], and [[extracellular matrix]] (ECM) components including collagens and [[glycosaminoglycans]], including [[hyaluronic acid]] and [[chondroitin sulfate]], all of which aid in the growth of the fetus.

===Volume===
The volume of amniotic fluid changes with the growth of fetus. From the tenth to the 20th week it increases from {{convert|25|to|400|ml}} approximately.<ref name="Amniotic Fluid: Not Just Fetal Urin">{{cite journal|last1=Underwood|first1=Mark A|last2=Gilbert|first2=William M|last3=Sherman|first3=Michael P|title=Amniotic Fluid: Not Just Fetal Urine Anymore|journal=Journal of Perinatology|date=24 March 2005|volume=25|issue=5|pages=341–348|doi=10.1038/sj.jp.7211290|pmid=15861199|doi-access=free}}</ref> Approximately in the 10th–11th week, the breathing and swallowing of the fetus slightly decrease the amount of fluid. Neither urination nor swallowing contributes significantly to fluid quantity changes until the 25th week when keratinization of skin is complete; then the relationship between fluid and fetal growth stops. It reaches a plateau of {{convert|800|ml}} by the 28-week [[Gestational age (obstetrics)|gestational age]]. The amount of fluid declines to roughly {{convert|400|ml}} at 42 weeks.<ref name="Amniotic Fluid: Not Just Fetal Urin"/> Some sources indicate about {{Convert|500|to|1000|ml}} of amniotic fluid is present at birth.<ref name=LARSEN2001 /><ref>{{Cite journal|last=Caroline|first=Nancy L.|date=1977-01-03|title=Medical Care in the Streets|journal=JAMA: The Journal of the American Medical Association|volume=237|issue=1|pages=43–6|doi=10.1001/jama.1977.03270280045020|pmid=576129|issn=0098-7484}}</ref>

===Rupture of membranes===

The forewaters are released when the amnion [[Rupture of membranes|ruptures]].  This is commonly known as "water breaking." When this occurs during [[Childbirth|labour]] at [[Gestation|term]], it is known as "spontaneous rupture of membranes". If the rupture precedes labour at term, however, it is referred to as "pre-labour rupture of membranes." Spontaneous rupture of membranes before term is referred to as "premature rupture of membranes." 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.<ref>[http://www.babyworld.co.uk/faq/individualfaq.asp?Section=Pregnancy&SubSection=Your+body&query=&opt=&page=&question=1711 Forewaters and hindwaters in Q&A section at babyworld.co.uk] {{webarchive|url=https://web.archive.org/web/20071009220104/http://www.babyworld.co.uk/faq/individualfaq.asp?Section=Pregnancy&SubSection=Your+body&query=&opt=&page=&question=1711 |date=2007-10-09 }}</ref>