Amniotic Fluid

Subject: Midwifery I (Theory)

Overview

Amniotic fluid may be the consequence of both maternal and fetal contributions. At 8 weeks of pregnancy, amniotic fluid is found, and its typical amount fluctuates with age. The fluid is pale straw in color and is composed of water 98-99% and solid 1-2%. It allows the fetus to move freely, works as a shock absorber, has nutritious value, contains antibiotics and gammaglobulin, and is the finest natural cervix dilator.

  • It is the outcome of contributions from both maternal and fetal origin. The following mechanism has been proposed for cases with amniotic fluid:
  • Maternal circulation transudation through placenta surface and fetal membrane.
  • Amniotic epithelial active secretion is to be done.
  • Transudation over an umbilical cord's surface and fetal placental circulation.
  • Fetal urine also makes a contribution.
  • At the 20th week of gestation, trachea-bronchial secretion and transfer over fetal skin prior to keratinization is suggested.

The amount of amniotic fluid rises as the fetus grows. It roughly grows from 25ml to 400ml from the 10th to the 20th week. The fetus's breathing and swallowing reduce the amount of fluid slightly around the 10th week, but neither peeing nor swallowing contribute significantly to fluid quantity changes until the 25th week, when skin keratinization is complete. Then the link between fluid and fetal growth breaks off. By 28 weeks, it had reached a plateau of 800ml. At 42 weeks, the fluid level drops to around 400 ml. At birth, around 1L of amniotic fluid is present.

Physical properties of amniotic fluid

The fluid is light straw in color or tubid, somewhat alkaline, and has a specific gravity of 1.010. It has a significant hypotonicity to maternal serum.

Composition of amniotic fluid

At term, amniotic fluid is 98% to 99% water and 1 to 2% solid. The solution is made up of organic substances such as:

  • Protein – 0.3mg%
  • Glucose – 20.0mg %
  • Urea – 30.0mg%
  • Uric acid- 40mg%
  • Creatinine – 2mg%
  • Total lipid – 50mg%

Amniotic fluid contains hormones, enzymes, inorganic substances such as sodium, chloride, potassium, and suspended particles such as epithelial cells, vernix caseosa, exfoliated amniotic epithelial cells, and so on.

Abnormal appearance

Under some conditions, the natural pale straw hue may be changed. Because of the presence of vernix caseosa, it may seem murky. The following are examples of abnormal appearance:

  • Greenish:
    This color is seen because of the presence of meconium, this is an indication of previous or present fetal discomfort in a position other than breech or transverse lay.
  • Golden yellow:
    This color is seen because of the presence of bilirubin as a result of fetal cell hemolysis caused by RH-incompatibility.
  • Dark maroon:
    This hue is caused by changed blood in an unintentional bleed.
  • Blood stained:
    Freshly blood stained and bright red in vasa Previa or low lying placenta will cause this abnormal appearance.

Function of amniotic fluid

Following are the functions of amniotic fluid:

  • Fluid allows the fetus in the uterus to move freely.
  • It works as a shock absorber, preventing potentially dangerous pressure on the embryonic tissues.
  • Liquor amnii inhibits the formation of adhesions between fetal components and amnion.
  • Allows for sufficient uterine cavity expansion, preventing excessive traction and providing proper placental and fetal circulation.
  • Swallowed liquor may have a nutritive value.
  • Swallowed liquor may include gammaglobulin and antibiotics, resulting in passive immunity.
  • During labor, the amniotic fluid and fetal membrane form a water bag that contains the fore waters and acts as a fluid wedge, acting as the finest natural cervix dilator.
  • It acts as the pool where the fetus excretes pee.
  • Bacterial activity safeguards the fetus from infection. Amniotic fluid is not a static fluid; it is refilled every 2.9 hours.

 

REFERENCE

Medline Plus. 05 January 2017 https://medlineplus.gov/ency/article/002220.htm

Pregmed. 19 August 2013. <http://www.pregmed.org/amniotic-fluid.htm>.

Jones, D.L., 1973, Fundamentals of obstetrics and gynecology Volume 1, Obstetrics, reprint first edition, Derek Llewellyn Jone, 1969.

Dutta, D.C. 1998, textbook of obstetrics, 4th edition, New central book agency PVT LTD, India.

Tuitui R. 2002, A textbook of Midwifery A (Antenatal), 3rd edition, Vidyarthi Pustak Bhandari (Publisher and Distributor), Bhotahity, Kathmandu
Things to remember
  • It is the outcome of contributions from both maternal and fetal origin.
  • The fetus's breathing and swallowing reduce the amount of fluid slightly around the 10th week, but neither peeing nor swallowing contribute significantly to fluid quantity changes until the 25th week.
  • Amniotic fluid is 98-99% water and 1-2% solid at term.
  • Amniotic fluid contains hormones, enzymes, inorganic substances such as sodium, chloride, potassium, and suspended particles like as epithelial cells, vernix caseosa, exfoliated amniotic epithelial cells, and others.
  • During labor, the amniotic fluid and fetal membrane form a water bag containing the fore waters, which operate as a fluid wedge, giving the finest natural cervix dilator.
Questions and Answers

Amniotic fluid

It is the outcome of contributions from the mother and the fetus. The suggested mechanism is as follows:

  • Transudate from the fetal membrane and placenta surface caused by the maternal circulation
  • Active amniotic epithelium secretion
  • Umbilical cord transudate and fetal placental circulation are also affected.
  • Contribution from urine from the fetus.
  • Fetal skin is exposed to trachea-bronchial secretion and transfer before the skin keratinizes at the 20th week of pregnancy.

The size of a fetus causes an increase in amniotic fluid volume. From the tenth to the twentieth week, it rises from 25 to about 400 milliliters. [Reference required] Beginning about the 10th week, the fetus's breathing and swallowing marginally reduce the amount of fluid, but until the 25th week, when skin keratinization is complete, neither urine nor swallowing considerably affect fluid quantity. After that, the connection between fluid and fetal growth is lost. By 28 weeks of gestation, it achieves a plateau of 800ml. At 42 weeks, the fluid level drops to about 400 ml. At birth, there is around 1L of amniotic fluid.

  • Physical Properties
    • The liquid has a low specific gravity of 1.010, is tubid, and has a light alkaline color. Maternal serum is severely hypotonic to it.
  • Composition
    • Amniotic fluid at term contains 98–99% water and 1%–2% solids. The organic substances in the solution include things like:
  • Protein
    • 0.3mg%
  • Glucose
    • 20.0mg %
  • Urea
    • 30.0mg%
  • Uric Acid
    • 40mg%
  • Creatinine
    • 2mg%
  • Total Lipid
    • 50mg%

Amniotic fluid contains a hormone, an enzyme, inorganic compounds like sodium, chloride, and potassium, as well as suspended particles like epithelial cells, vernix caseosa, exfoliated amniotic epithelial cells, etc.

Abnormal Appearance

In some situations, the typical pale straw tint may change. Due to the vernix caseosa's presence, it could seem turbid. The following are examples of abnormal look.

  • Greenish
    • Due to the presence of meconium, a sign of fetal discomfort in a presentation other than breech or transverse lying, in the past or present.
  • Golden Yellow
    • Because of the presence of bilirubin brought on by the hemolysis of fetal cells brought on by RH-incompatibility.
  • Dark Maroon
    • Because of altered blood in an unintentional bleeding
  • Blood Stained
    • Bright red and freshly bloodied in the vasa Low-lying placenta, or previa

Function of Amniotic Fluid

  • The fetus can move freely in the uterus thanks to fluid.
  • Since it serves as a shock absorber, dangerous pressure on the fetal parts is avoided.
  • Between fetal components and the amnion, liquor amnii prevents the establishment of adhesion.
  • Expands the uterine cavity sufficiently to prevent severe traction and to ensure adequate placental and embryonic circulation.
  • Drinking alcohol may have some nutritive nutrients.
  • Passive immunity is provided by ingested alcohol, which may also contain antibiotics and gammaglobulin.
  • The amniotic fluid and fetal membrane, which together make up the water bag that holds the fore waters during labor and functions as a fluid wedge to dilate the cervix, are the best natural dilators known to man.
  • Provides the reservoir for the fetus's urine excretion.
  • The fetus is protected from ascending infection by bacterial action. Amniotic fluid circulates dynamically and is replaced every 2.9 hours; it is not a static fluid.

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