What Is Amniotic Fluid? – Composition, Functions & Levels

By (embryologist) and (fertility counselor).
Last Update: 04/15/2014

The amniotic fluid is contained within the amniotic sac, and its main functions are to surround and cushion from bumps and injury the unborn embryo by creating an environment for him.

Provided bellow is an index with the 3 points we are going to expand on in this article.


It begins to form up to two weeks of pregnancy. At first it is mainly made of water, but as the pregnancy process develops, proteins, carbohydrates, sugars and electrolytes are incorporated in order to help the fetus development, although its main component is fotal urine.

It is made up from fetal urine and the amniotic cavity cells. The circulating fluid is ingested and constantly expelled by the fetus so that it is renewed. The amniotic fluid reaches its maximum volume of 800 ml at about 34 weeks, while during week 40 it volumes an average of 600 ml.


Its main functions are:

  • To protect the embryo or foetus against external bumps or sudden movements.
  • To cushion the foetus' movements so that they are not painful for the mother.
  • To give shelter to the embryo so that temperature changes within the mother's body do not affect him.
  • To allow the foetus to move around, therefore preventing the amniotic sac wall from sticking to him.
  • To allow the proper development of the lungs.

Amniocentesis, also known as amniotic fluid test or AFT, is a prenatal test which consists of withdrawing a small sample of amniotic fluid in order to analyse the foetus genetic information.

Alterations within the amount of amniotic fluid may require additional pregnancy check-up.

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 Neus Ferrando Gilabert
Neus Ferrando Gilabert
B.Sc., M.Sc.
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information about Neus Ferrando Gilabert
Adapted into english by:
 Sandra Fernández
Sandra Fernández
B.A., M.A.
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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