Amniotic fluid: what it is, function, normal volume and more

There are several structures and substances necessary for the full development of the fetus during pregnancy. Among them, there is amniotic fluid , which is what fills the bag in which the baby is “immersed” in the womb during pregnancy.

Then, you can better understand the importance of this fluid, its characteristics, how to identify it and some information about its levels. Check out:

What is amniotic fluid?

Amniotic fluid is a fluid that is inside the amniotic sac , that is, the place where the fetus is throughout pregnancy. In this sense, it is a liquid that involves the baby throughout its development process, until the moment of delivery.

It allows the fetus to move in the uterine cavity, protects the baby from possible trauma suffered by the mother and protects him from bacterial infections. In addition to other issues that directly contribute to full fetal development.

Regarding how the amniotic sac and the liquid that make it up are formed, basically what occurs is the formation of this structure in the 2nd week of pregnancy. Being produced by the placenta and membranes until the 4th gestational month.

After this period, the fetus ingests the amniotic fluid, so that, after being swallowed, the content is processed and eliminated as urine, which is possible due to the fact that there is already a maturation of its urinary system. With this, the baby’s urine becomes the main component of the amniotic fluid.

Then, it stops being similar to the mother’s blood plasma (its initial composition) and starts to have other components: hormones, cytokines and essential nutrients.

In addition, it also consists of a small amount of pulmonary secretions, since the baby sucks in the fluid and also exhales. This also causes this fluid to be constantly renewed (approximately every 4 to 6 hours).

Finally, it should be noted that the volume of the liquid increases up to 34 to 37 weeks of gestation, then gradually decreases until the moment of delivery.

What is amniotic fluid for?

The functions of amniotic fluid are related to fetal development. Therefore, it has the role of helping in the nutrition, maturation and protection of the baby while it is in the mother’s womb. Thus, their contributions are as follows:

  • Protects the fetus against external trauma suffered by the mother;
  • Avoids compression of the umbilical cord;
  • Protection against infections;
  • Ensures stability in uterine temperature;
  • It collaborates with the musculoskeletal development and allows the movement of the fetus in the uterus;
  • Assists lung development;
  • Helps in the maturation of the digestive and urinary systems.

Therefore, it is the amniotic fluid that supports the development of the fetus during pregnancy.

What is the normal volume of amniotic fluid?

It is important to know that the volume of amniotic fluid varies during pregnancy, according to the needs of each phase. At first, it is a small amount due to the fact that the fetus is also in a smaller size.

Thus, the volume of the liquid gradually increases, as the baby grows. This process reaches its maximum point at around 34 gestational weeks, which is when the fluid begins to decrease (until the moment of delivery).

During this period, the volume of up to 1000mL of amniotic fluid can be reached. The amount is measured by ultrasound , so this is a periodic examination during the prenatal phase, making it possible to monitor this fluid and fetal development.

So, there is no fixed “normal volume” with respect to the levels of this solution. This, since it varies according to each period of pregnancy and according to the size of the baby.

However, there may be an inadequate decrease or increase in what is expected for the gestational phase. In these cases, oligohydramnios is the phenomenon that characterizes the decrease in amniotic fluid and polyhydramnios when there is an excess.

Causes for the oligoidrâmnio

It is not known exactly the reasons that lead to the decrease in amniotic fluid (phenomenon called oligohydramnios), however, it is indicated that this may be related to factors such as:

  • Maternal dehydration (leads to a general decrease in fluids in the woman’s body);
  • Rupture in the amniotic pouch (supports the fetus and stores the amniotic fluid), causing loss of fluid through the vaginal cavity;
  • Use of certain medications (such as for hypertension, for example);
  • When the pregnancy lasts longer than expected (the fluid decreases, since the baby should have been born).

In cases such as the pregnancy time that is longer than normal, it may be necessary to perform a cesarean section. This, since amniotic fluid is essential for the baby, so that its drastic decrease could even cause the child to die.

In addition, oligohydramnios may be related to developmental problems . Since most amniotic fluid is formed by the baby’s urine, if there is any malformation (especially in the urinary system), it can interfere with fluid production.

Causes for polyhydramnium

Not only can the decrease in amniotic fluid cause complications for the mother and baby, but levels above normal can also be harmful. When this occurs, the cause may be linked to factors such as:

  • Mother with diabetes mellitus;
  • Twin pregnancy;
  • Congenital abnormalities of the baby;
  • Chromosomal disorder.

Thus, the need to perform prenatal care in an adequate manner is reinforced, by carrying out exams such as ultrasound. Thus, making it possible to identify possible problems and complications that can affect the health of the baby and even the mother.

What is the color of the amniotic fluid?

Know the color of the amniotic fluid

The color of the amniotic fluid serves as a way of indicating the baby’s health conditions and even the urgency of delivery. Since it is only possible to know this coloring at the moment of birth, when breaking the bag it is necessary to observe this characteristic.

Some doctors even recommend that the mother, while going to the maternity hospital, use an absorbent (preferably a larger size, due to the amount of liquid). Thus, when arriving at the hospital, it will be possible for the professional to analyze the color.

Better understand what are the possible colors and what each means, respectively:

  • Transparent or whitish – natural color, the liquid may also contain some white lumps (usually formed by small pieces of hair, fat and skin of the fetus);
  • Red – may indicate the placental detachment, which could compromise the passage of nutrients and oxygen to the fetus. In some cases, it may be necessary to perform a cesarean section in order to preserve the baby’s health and life;
  • Dark green – the liquid is thicker (thicker), which indicates that the fetus has evacuated in the uterus. Follow-up after delivery is necessary, in addition to cleaning, since if the baby aspirates these substances, he may suffer obstruction of the trachea and airways;
  • Yellow – indicates the possibility of feet in the uterine cavity, which should be analyzed by the doctor to identify the cause. However, in some cases, this staining may simply be due to a higher concentration of urine from the fetus;
  • Brown – in the vast majority of cases, it characterizes an emergency situation , as it may indicate severe bleeding or even fetal death.

How to identify or amniotic fluid?

Some women may find it difficult to identify the rupture of the bag. It is at this moment that the release of the amniotic fluid occurs, so knowing how to identify it can help to confirm that the “bag has burst” and that it is time to go to the maternity hospital.

For this, pay attention if the liquid is colored (transparent / whitish, red, green, yellow or brown). When it is in its normal aspect, that is, without color (transparent or whitish), it is easier to confuse it with urine, for example.

In addition, the amniotic fluid has a characteristic smell (it may somewhat resemble the smell of bleach) and also a larger volume than urine.

Thus, although the nerves may be “on edge” at the time of the rupture of the bag, knowing these details can facilitate the identification of the liquid.

Low amniotic fluid: how to increase it?

There is no specific treatment to increase amniotic fluid when it is at lower than normal levels throughout pregnancy. However, some precautions can be recommended to avoid further decrease.

Thus, the doctor may ask the mother to considerably increase her daily fluid intake and rest – sometimes almost absolute.

If the amniotic fluid is in very low levels at a stage closer to the end of pregnancy, it may be that the obstetrician chooses to anticipate delivery in order to avoid complications to the baby’s health.


Pregnancy is a phase that brings many new features to the mother’s life, especially when it comes to the first child. Therefore, it is important to seek secure information and clarify doubts with the doctor regarding all details.

And in the ” Pregnancy ” tab here of Hickey solution you can find more content like this!

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