Amniotic fluid

During pregnancy, the product of conception (first embryo then fetus) develops inside the uterus. About 12 days after conception, the amniotic sac forms inside the uterus, completely filled with amniotic fluid, which will keep the unborn child in place for the entire duration of the pregnancy.

Initially the amniotic sac is composed largely of water deriving from the mother’s body, and this is probably the cause of the strong sensation of thirst that affects pregnant women  during the 1st trimester . In addition to water (about 98%), the amniotic fluid is composed of mineral salts and cells of the fetus (2%).

After about 4 months, i.e. around the  20th week of pregnancy , the embryo develops kidneys and is therefore already able to produce its own urine. It is also able to swallow and digest amniotic fluid. The amniotic fluid will eventually consist mostly of the urine of the embryo: which may seem revolting to us, but for the baby this is no problem. Apart from urine, amniotic fluid contains nutrients, hormones and antibodies.

The main functions of the amniotic fluid

  • Provides the enzymes necessary for the development of the unborn child . Amniotic fluid is a perfectly balanced element, rich in carbohydrates, electrolytes, enzymes, hormones, lipids, lactate, proteins, peptides and pyruvate.
  • It offers mechanical protection to the unborn child . One of the main functions of the amniotic fluid is to protect the future baby from mechanical trauma, absorbing shocks of all kinds, and keeping it unharmed inside the belly. The amniotic fluid provides a well-lubricated environment where it can move freely, thus promoting its growth and strengthening of its bones.
  • It allows the development of all parts of his body . The amniotic fluid circulates freely inside the belly, keeping all parts of the baby’s body lubricated. This allows its outermost structures, such as toes and fingers, to grow and prevents them from sticking together. It also helps develop your baby’s lungs and digestive system.
  • It keeps the temperature of the embryo of the fetus constant .
  • It prevents the baby from crushing the umbilical cord .
  • It represents a natural immune system . Amniotic fluid plays an important role in protecting the baby. Many of the antimicrobial substances that make up the immune system are in fact found in the amniotic fluid and protect the baby from pathogens such as bacteria, fungi, protozoa and viruses.
  • It is a diagnostic tool . Amniotic fluid helps doctors assess the health of the future baby. Starting from the 70s of the past century, a very useful means of identifying – chromosomal anomalies – neural tube defects – genetic diseases – and many other congenital problems of the blood and metabolism, is constituted by a particular examination – the amniocentesis – which  provides that the amniotic fluid is taken .

Imbalances in amniotic fluid levels

The level of amniotic fluid is well regulated by the mother’s body and by the exchange of fluids with the baby which takes place in the uterus. In most pregnancies, this complex regulating process works perfectly. There are, however, some rare occasions when something is wrong, and the amniotic fluid level rises or falls excessively. Let’s see what they are.

  • Oligohydramnios  – It is a condition of pregnancy which is characterized by too little amniotic fluid. Only 4% of pregnant women develop this condition. The causes can be many and include: dehydration, late pregnancy, high blood pressure or diabetes, rupture of the fetal membranes, some problems with the development of the kidneys or the urinary tract of the child, problems with the placenta. Oligohydramnios is not a condition that a pregnant woman can detect on her own: it can only be diagnosed during an ultrasonography.
  • Polyhydramnios  – Polyhydramnios is a condition of pregnancy in which the level of amniotic fluid is too high. It is very rare, occurring in 1-2% of pregnancies. Most women who are diagnosed with polyhydramnios have problems and will carry a normal pregnancy to term. Polyhydramnios is a condition that develops gradually, so you may not notice any particular symptoms. It is usually diagnosed by doing an ultrasonography, towards the  final stage of pregnancy .

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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