Very Interesting Facts About Amniotic Fluid

Amniotic fluid has a very important role in fetal development and well-being during pregnancy. Besides being a protective agent, it stores nutrients and allows fetal musculoskeletal, gastrointestinal, and lung development.
Very Interesting Facts About Amniotic Fluid
Sara Viruega Encinas

Written and verified by the pharmacist Sara Viruega Encinas.

Last update: 27 December, 2022

Amniotic fluid is the fluid that surrounds the fetus during gestation inside the womb. It exerts a very important role in fetal growth and development. In this article, discover some very interesting facts about amniotic fluid that you might not have known.

Amniotic fluid composition

This fluid changes its composition as the pregnancy progresses. Furthermore, its volume increases as pregnancy progresses, generally until week 32. However, it begins to decrease at week 40.

Initially, it’s the result of osmotic gradients. In other words, it’s first formed by plasma from maternal blood and substances from the placenta, uterine membrane, and the surface of the embryo.

Then, once the fetus has developed urination and swallowing mechanisms, it’s mainly formed by:

  • Fetal urine.
  • Fluid from the lungs.
  • Oral and nasal secretions.
Very Interesting Facts About Amniotic Fluid

The fetus is continuously ingesting this liquid and, at the same time, expelling it through urine. This involves the regulation of the amount present in the amniotic sac, which grants the necessary balance.


Some of the most important amniotic fluid functions are:

  • Protective function against external trauma or shock.
  • Cushioning effect for the fetus and the umbilical cord in the womb.
  • Protection and defense against infection.
  • Deposit of food and growth factors for the fetus during pregnancy.
  • It helps maintain fetal temperature stable.
  • In addition, it contributes to lung maturation thanks to the presence of several enzymes.
  • Also, it allows fetal musculoskeletal, gastrointestinal, and lung development.

Alterations in the amount of fluid

During pregnancy, there can be variations in the amount of amniotic fluid, causing either too much or not enough fluid, for various reasons. Both are pathological:

  • Oligohydramnios. Amniotic fluid deficiency. This condition is associated with complications, such as:
    • Early labor induction.
    • Low birthweight.
    • Fetal bradycardia during delivery.
    • It can even cause fetal death.
  • Polyhydramnios. An excess of amniotic fluid. This condition is associated with complications, especially maternal, such as:
    • Gestational diabetes.
    • Hypertension during pregnancy.

Medical professionals usually detect these alterations by an ultrasound procedure to measure the volume of amniotic fluid. They do so through the amniotic fluid index (AFI).

To get this information, the expert divides the uterus into four unobstructed quadrants, which they measure in centimeters. A normal AFI is between 3 to 8 inches (8 and 21 cm).

Amniotic fluid embolism

Another related pathology is amniotic fluid embolism. It occurs when the amniotic fluid enters the woman’s blood. This is a very serious condition that can cause systemic hypoxia and coagulation abnormalities.

Very Interesting Facts About Amniotic Fluid

Meconium-stained amniotic fluid

Finally, we decided to highlight another aspect to consider. Meconium-stained amniotic fluid consists of the presence of meconium in the amniotic bag. Meconium is an infant’s earliest stool. Generally, it occurs after birth.

But sometimes, especially in babies who stay inside the womb for longer, it can occur before birth.

Typically, when the mother’s water breaks, the liquid is transparent or yellowish. If, on the other hand, it’s opaque, greenish, or thick, it indicates the presence of meconium. In that case, the specialist should assess the situation, as it can be an indicator of fetal distress.


Amniotic fluid has a very important role in the fetus’ development and well-being during pregnancy. Besides being a protective agent, it stores nutrients and allows musculoskeletal, gastrointestinal, and lung development. Any amniotic fluid alteration can cause major damage.

In addition, its prenatal study and analysis can detect congenital defects, such as chromosome disorders. This is performed through an amniocentesis. However, this technique is also associated with major risks that the medical professional must evaluate before performing it on a patient.

We hope you’ve found these facts about amniotic fluid to be interesting!

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Morgan-Ortiz, F., Morgan-Ruiz, F. V., Quevedo-Castro, E., Gutierrez-Jimenez, G., & Báez-Barraza, J. (2015). Anatomía y fisiología de la placenta y líquido amniótico. Rev Med UAS5(4).
  • Cerviño, N., & Pagés, G. (2004). Patología del líquido amniótico. Rev Chil Obstet Ginecol69(6), 276-482.
  • Blair, J. E. S., & Calle, A. M. C. (2007). Alteraciones del líquido amniótico, enfoque diagnóstico y terapéutico. Memorias Curso de Actualización en Ginecología y Obstetricia15, 57.
  • Reyes, E. R., González, G. K. S., Hidalgo, A. O., Peña, Y. R., & Regueiro, A. F. (2015). Resultados de seis años de estudios citogenéticos en líquido amniótico. Revista Electrónica Dr. Zoilo E. Marinello Vidaurreta40(11).

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.