By Neus Ferrando Gilabert BSc, MSc (embryologist).
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.

The different sections of this article have been assembled into the following table of contents.


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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Authors and contributors

 Neus Ferrando Gilabert
BSc, MSc
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
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