Amniotic fluid is involved in the child’s metabolism and protects him from injury, and its examination helps to identify deviations from the norm.
40 days after fertilization, a fetal bladder is formed around the embryo, consisting of two membranes - the chorion (external) and the amnion (internal). The amnion produces fluid that accumulates and is renewed, which is why it is called amniotic. Amniotic fluid is partially produced by the body of the mother and fetus, depending on the duration of pregnancy, it contains albumin (the main protein in the blood plasma), fats, organic and inorganic salts, hormones, enzymes and vitamins, and epithelial cells.
Water, like the amniotic sac, protects against mechanical damage, infections, temperature fluctuations and other unfavorable irritants; in addition, they participate in the metabolism between mother and child. Thanks to amniotic fluid, the functioning of the baby's urinary tract and lungs is improved. Renewal occurs every three hours with the help of amnion cells, part of which is absorbed by the mother’s body through the umbilical cord, so the fidget always swims in a clean “pool”.
The amount changes as the pregnancy progresses - by the end of the first trimester about 100 ml, in the third trimester up to 1.5 liters; problems such as polyhydramnios or oligohydramnios are equally dangerous for the fetus. The deficiency indicates problems with the kidneys of the mother or baby; on the part of the woman, this problem is often provoked by gestosis or diseases of the blood vessels. Children with oligohydramnios are born with low body weight, are at risk of hypoxia during childbirth, and may have breathing problems after birth.
An excess indicates poor functioning of the gastrointestinal tract and kidneys in the fetus. In case of serious violation of the norm, appropriate treatment is carried out (amnioreduction).
| Gestational age | Normal amniotic fluid in cubic cm |
| 17 | 12,2 |
| 18 | 12,8 |
| 19 | 13,4 |
| 20 | 13,8 |
| 21 | 14,2 |
| 22 | 14,4 |
| 23 | 14,7 |
| 24 | 14,8 |
| 25 | 14,8 |
| 26 | 14,8 |
| 27 | 15,7 |
| 28 | 14,7 |
| 29 | 14,6 |
| 30 | 14,4 |
| 31 | 14,3 |
| 32 | 14,3 |
| 33 | 14,2 |
| 34 | 14,1 |
| 35 | 14,1 |
| 36 | 13,5 |
| 37 | 13,2 |
| 38 | 13 |
The volume, composition and type of amniotic fluid has important diagnostic significance. The volume is measured using ultrasound at 20-22 weeks of pregnancy, the sum of the measurements is designated in centimeters as “AFI”. The correct value is in the range of 5-20, a value less than 5 indicates oligohydramnios, more than 20 indicates polyhydramnios. Only a doctor can make an accurate diagnosis; slight fluctuations from the average are possible. A visual assessment of the water is carried out using an amnioscope inserted into the woman’s cervical canal, which allows the color and volume to be assessed.
Amniocentesis is performed in extreme situations. A sample of amniotic fluid (15-20 ml) is taken through a puncture of the abdominal wall and uterus with a thin needle, after which it is subjected to various tests. The study shows the absence or presence of fetal infections, genetic diseases of the fetus, and the degree of lung maturity is assessed.
The norm of amniotic fluid is disrupted for weeks when there is leakage; this symptom requires special attention and an immediate visit to the doctor’s office. How to distinguish water from vaginal discharge or urine? Amniotic fluid has a weak specific odor or no odor at all; at the beginning of pregnancy it is clear, but closer to childbirth it becomes cloudy. A change in color to brown, greenish or yellow indicates an emergency situation where urgent hospitalization is necessary.
Green color indicates severe hypoxia, brown indicates the death of the baby. A yellowish color is normal for the last trimester. Pinkish water after the 38th week of pregnancy is a harbinger of labor; before the 38th week - placental abruption or other problems leading to internal bleeding in the mother or baby.
Leakage leads to infection of the fetus; emergency medical attention is required!
Amniotic fluid (amniotic fluid) is a biologically active liquid medium that surrounds the fetus during pregnancy. It consists of water and contains small amounts of mineral salts, fetal cells, fragments of sebaceous glands and epidermal scales. The formation of amniotic fluid begins in the third week of pregnancy and reaches 1-1.5 liters by the time of birth.
Amniotic fluid not only allows the baby to move freely in the womb, but also maintains a constant body temperature and protects it from infection and mechanical influences from the external environment. Towards the end of pregnancy, the kidneys and lungs of the unborn child begin to take part in the production of amniotic fluid.
Invasive diagnostics of amniotic fluid includes:
Amnioscopy. During amnioscopy, a tube with a flashlight (amnioscope) is inserted into the cervix. When illuminating the amniotic fluid, you can examine its color and consistency, as well as the presence of blood or feces in it. Amnioscopy is performed after 37 completed weeks of pregnancy.
Amniocentesis. Amniocentesis is the collection of fetal fluid by puncture of the amniotic membranes. The puncture is performed through the abdominal cavity, or through the vaginal wall or cervix. With amniocentesis, it is possible to determine the composition of amniotic fluid and thereby identify pathology in the unborn child. Performed according to indications after 16 weeks. After taking amniotic fluid, bacteriological, histological, cytogenetic, and biochemical analyzes are performed.
The change in IAF has a certain pattern. From the beginning of pregnancy to the 27th week of gestation, the amniotic index gradually increases and averages 156 mm, then it declines. The amniotic fluid index is reduced by approximately 10 mm compared to week 27.
The amniotic fluid index at 37 weeks, which is very close to childbirth, decreases by another 10 mm. Immediately before the birth of the child (38-40 weeks of gestation), a final decrease in the amniotic fluid index is observed to an average value of 125 mm.
Attention! Routine ultrasound and determination of AFI help to timely diagnose abnormalities in the amount of amniotic fluid and prescribe effective treatment to prevent various pathologies in the unborn child.
Objectively, the amniotic fluid index is determined by dividing the uterus into 4 squares, the vertical axis of the marking passes through the center of the abdomen, the horizontal through the navel. In each quarter, the maximum pocket is determined - the space where amniotic fluid is located without a child. Next, these indicators are summed up and the amniotic index is displayed - the result of adding the obtained values.
Norms of amniotic fluid index by week in table form
When fetal oligohydramnios is severe or there are abnormalities on CTG, symptomatic therapy is used:
During the treatment process, constant monitoring of the fetal condition using CTG is necessary, since with this pathology there is a possibility that the unborn child will become entangled in the umbilical cord. If conservative therapy is ineffective, amniocentesis is used - taking a small amount of amniotic fluid, or premature delivery.
Pregnancy is considered the best period in every woman's life. Waiting for the birth of a small miracle instills happiness and fills life with bright colors. However, in addition to positive emotions, women also experience others associated with fear and ignorance of many processes that occur in a pregnant woman’s body. What are the norms for the amniotic fluid index by week? This is one of the questions that women think about. Let's look into it, because the values of the indicator (abbreviated designation - IAF, IOV) determine the condition of the fetus.
During pregnancy, the fetus develops in the uterus. It is surrounded by membranes and fluid, which acts as a natural environment for the fetus. It protects it from mechanical damage, creates conditions for movement and proper location in the uterus. Each period of pregnancy is characterized by a certain volume of fluid. Taking this into account, specialists make diagnoses about the presence of certain diseases in the fetus.
In the first trimester, the volume of water surrounding the embryo is determined by the function of the female body. Subsequently, the fetus begins to influence the amount of fluid. It is swallowed by him and excreted in the urine. When natural processes are disrupted, the volume of liquid changes up or down. Normally, at week 18 this figure is 300 ml. By the 34th week it increases to 800 ml. As labor approaches, the fluid volume decreases to 600 ml.
There are several ways to find out the volume of amniotic fluid. The first one is subjective. During an ultrasound, a specialist can identify deviations from the norm based on some signs and characteristics:
When using a subjective method, you can make mistakes. That is why J. Phelan proposed the calculation of the IAF. The studies carried out made it possible to determine the norms of the amniotic fluid index by week. When comparing them with the values obtained from examinations of pregnant women, one can judge the presence of a lack or excess of water.
In order to determine whether the volume of amniotic fluid is normal, specialists measure a special index. This is done during ultrasound examinations. The specialist performs the following actions:
The index is measured in centimeters or millimeters. The value obtained by adding the vertical depths is approximate. Despite this, it can accurately identify excess (polyhydramnios) or deficiency (oligohydramnios) of amniotic fluid.
For the first time, a pregnant woman goes for a routine ultrasound in the first trimester. For this period, the norms for the amniotic fluid index by week have not been determined, because the fetus is very small. Scanning is performed for slightly different purposes:
The woman undergoes the next ultrasound examination in the second trimester of pregnancy, which lasts from the 14th to the 26th week. At this time, various fetometric parameters of the fetus are determined. The amniotic fluid index is also calculated. The norm at 20 weeks and at other times in the second trimester is presented below in the table.
| Duration, in weeks | Indicator, in mm | ||||
| Percentile | |||||
| 97,5 | 95 | 50 | 5 | 2,5 | |
| 16-18 | 201-220 | 185-202 | 121-133 | 79-87 | 73-80 |
| 19-21 | 225-233 | 207-214 | 137-143 | 90-95 | 83-88 |
| 22-24 | 235-238 | 216-219 | 145-147 | 97-98 | 89-90 |
| 25-26 | 240-242 | 221-223 | 147 | 97 | 89 |
The last trimester of pregnancy lasts from the 27th week until the moment of birth. During this period, every pregnant woman undergoes a final ultrasound scan. This trimester is optimal for:
The table below shows the norms of the amniotic fluid index by week for the last trimester of the gestation period.
| Duration, in weeks | Indicator, in mm | ||||
| Percentile | |||||
| 97,5 | 95 | 50 | 5 | 2,5 | |
| 27-29 | 245-254 | 226-231 | Decrease from 156 to 145 | From 95 to 92 | From 85 to 84 |
| 30-32 | 258-269 | 234-242 | From 145 to 144 | From 90 to 86 | From 82 to 77 |
| 33-35 | 274-279 | 245-249 | From 143 to 140 | From 83 to 79 | From 74 to 70 |
| 36-38 | from 279 to 269 | from 249 to 239 | From 138 to 132 | From 77 to 73 | From 68 to 65 |
| 39-40 | from 255 to 240 | from 226 to 214 | from 127 to 123 | from 72 to 71 | from 64 to 63 |
Polyhydramnios in the medical literature is called excessive accumulation of amniotic fluid. During full-term pregnancy, their volume exceeds 1500 ml. Foreign sources indicate a figure equal to 2 liters. Polyhydramnios is determined very easily by the index. This pathology is characterized by an increase in the numerical values of the indicator above the 97.5 percentile. For example, the normal amniotic fluid index at 32 weeks can reach a maximum of 269 mm. For cases in which the IAF is greater than this figure, an excess of water is typical.
Polyhydramnios is divided by experts into acute and chronic. The first form of the pathological condition is diagnosed at 16-27 weeks. It is considered extremely rare. The most common form of polyhydramnios is chronic. It is detected in women, usually in the third trimester of pregnancy. The chronic form is characterized by a blurred clinical picture.
The amniotic fluid index exceeds the norm at 30 weeks and at other times for various reasons. They are associated with inflammatory and infectious diseases of a pregnant woman, pathologies of the fetus (for example, intrauterine infections, hereditary diseases, chromosomal abnormalities, developmental disorders of the digestive system, central nervous system), pathologies of the placenta.
In medicine, oligohydramnios is considered to be a reduction in water volume to 500 ml or less during full-term pregnancy. Foreign sources indicate a figure characterizing this pathology - 300 ml. The diagnosis of “oligohydramnios” is made by doctors in cases where AFI values are below the 5th percentile. For example, 80 mm is the amniotic fluid index at 26 weeks. It doesn't meet the norm. This is pronounced oligohydramnios.
The causes of oligohydramnios are associated with congenital malformations of the fetus, due to which urine is not excreted in normal quantities from the body. Such pathologies include renal agenesis and bilateral multicystic renal dysplasia. In some cases, the causes of low AFI and oligohydramnios are fetal growth retardation, chromosomal abnormalities, intrauterine infections, chronic renal and cardiovascular diseases in women, preeclampsia, placental insufficiency, post-term pregnancy, and antenatal fetal death.
AFI is an important indicator. For example, comparing the calculated amniotic fluid index at 33 weeks with the norm does not simply allow us to record the presence of oligohydramnios or polyhydramnios. Thanks to the calculation of the indicator, it is possible to prevent the development of complications. Due to polyhydramnios, for example, the following may occur:
Oligohydramnios also has complications. It leads to intrauterine growth retardation, the appearance of adhesions, and an increased risk of perinatal death. Children born to women diagnosed with oligohydramnios often experience underdevelopment of the skeleton and lungs, and low body weight.
After comparing the amniotic fluid index with the norm at 31 weeks and at other times, after identifying oligohydramnios or polyhydramnios, doctors prescribe appropriate treatment and determine the management of pregnancy and childbirth. In some cases, termination of pregnancy is required. Indications for it are a combination of polyhydramnios or oligohydramnios with intrauterine malformations and an acute form of polyhydramnios that arose before
During pregnancy, an amniotic sac forms in the uterus, which will produce amniotic fluid. This fluid protects your baby. Reduced amniotic fluid is called oligohydramnios or oligohydramnios. A decrease in amniotic fluid can lead to problems, so it is very important to maintain normal fluid levels using medical or folk remedies. The article provides some tips on this topic.
The type of treatment is selected depending on the stage of pregnancy. Therefore, the doctor's choice of treatment will be based on the stage of pregnancy. Doctors usually prescribe one of the following treatments along with water restoration.
Injection with amniotic fluid. This injection is a syringe filled with leaked amniotic fluid, which the doctor injects back into the uterus, into the amniotic sac. This method can improve the condition of the pregnant woman. This procedure is very similar to amniocentesis (testing of amniotic fluid), but instead of taking a sample of amniotic fluid, the doctor injects the leaked fluid into the amniotic sac.
We administer fluid intravenously. Some pregnant women are admitted to the hospital to receive additional intravenous fluid therapy. This method is used if conventional means (for example, drinking large amounts of water) are not able to increase the amount of amniotic fluid. If you have tried increasing the fluid yourself and there is no change, you will most likely be given intravenous fluid.
Catheter to increase amniotic fluid. Amnioinfusion is the injection of Ringer's solution or normal saline solution into the amniotic sac using a catheter. This procedure will increase the level of amniotic fluid, which will better protect the baby and the umbilical cord.
Talk to your doctor about having a shunt placed in your body. Shunts are used to move fluid from one place in the body to another. In this case, a shunt directs fetal urine into your amniotic sac if the cause of low amniotic fluid is chronic fetal uropathy (kidney problems that reduce amniotic fluid).
Talk to your doctor about stopping taking ACE inhibitors if you are prescribed them. ACE inhibitors are medications that help lower high blood pressure by stopping the conversion of angiotensin I to angiotensin II in your body. These medications are generally harmless, but they should not be taken during pregnancy because they may reduce the amount of amniotic fluid.
What is amniotic fluid needed for? The most important function of amniotic fluid is to protect the child while he is in the womb. It plays the role of a pillow, protecting the child from blows. But it also performs other functions:
Let's get acquainted with the symptoms of decreased amniotic fluid. Oligohydramnios is a condition that occurs when the amniotic fluid is greatly reduced (below 300 ml). If you suspect the development of oligohydramnios, you should definitely talk to your doctor. If you think that a similar problem may appear in the future, you should familiarize yourself with the following signs:
You should be familiar with the risk factors that can lead to a decrease in amniotic fluid. Some of the most common reasons are described below:
The amniotic index is an indicator that characterizes the amount of amniotic fluid during pregnancy. Amniotic fluid is also called amniotic fluid: the liquid natural environment provides the baby with everything necessary for the formation of strong immunity from birth. Its volume has important diagnostic value when examining a woman during pregnancy.
The biological environment surrounding the fetus in the mother's womb is multifunctional - without it, the child cannot survive. Here's what's special about amniotic fluid:
As pregnancy progresses, the quantitative and qualitative indicators of amniotic fluid are constantly changing. Deviations of these numbers from the norm are of great importance for doctors - based on this information, one can assume the presence or absence of certain pathologies in the expectant mother. Timely diagnosis allows you to reduce the risk for a woman and her child even before birth or, in extreme cases, after the baby is born.
The amniotic fluid index (AFI) is an indicator that reflects how much amniotic fluid fills the amniotic sac at a given stage of pregnancy.
In addition, experts take into account other characteristics of the natural liquid environment in which the fetus develops:
Analysis of amniotic fluid using ultrasound allows you to diagnose two common abnormalities during pregnancy - oligohydramnios and polyhydramnios, and also take timely measures to eliminate them. During an ultrasound, a specialist will determine the amniotic fluid index and determine the multiplicity of the vertical pocket. If the indicators exceed the normal limits or, conversely, are less than them, the conclusion indicates polyhydramnios or oligohydramnios.
What is a vertical pocket and why is its size determined? The vertical pocket is the longest section of free water, which is located between the child and the anterior abdominal wall. It is undesirable for the limbs or umbilical cord of the fetus to be located in this area. Acceptable vertical pocket lengths are 5–8 cm.
To assess the volume of amniotic fluid using the amniotic fluid index, the gynecologist will divide the expectant mother’s belly into 4 sections, drawing two conditional perpendicular lines that intersect in the navel area. It will then determine the index values for the largest vertical pocket in each of the four zones. The final index value is calculated by adding up the indicators of all pockets.
The norm of the amniotic index is calculated by week, starting from 16 weeks. As the gestational age increases, the AFI indicators will also increase: the highest indicator will be at 32 weeks - 77 - 169 ml. The amniotic index norms are shown in the table.
If the AFI indicators do not coincide with the specific stages of pregnancy, the expectant mother is diagnosed with oligohydramnios or polyhydramnios.
This pathology accompanies childbearing quite often. The amniotic index with oligohydramnios is slightly or significantly underestimated. Moderate oligohydramnios is diagnosed when the volume of amniotic fluid differs slightly from the normal AFI. The situation can be corrected with the help of a special diet and adjustments to the daily routine, then the amount of water will soon return to normal and will not affect the child’s health in any way.
Oligohydramnios is considered severe if the amniotic fluid index during pregnancy is significantly less than the standard value. In this case, the pregnant woman is urgently sent to the hospital - there is too high a risk that the child will develop complications. Severe oligohydramnios can cause underdevelopment of vital organs and systems and significant curvature of the skeleton.
In addition, oligohydramnios threatens the child with a number of other complications, including:
When a significantly reduced IAF is discovered at a long term (30–34 weeks), serious pathologies of the child’s development are most likely already present, so the question of artificial termination of pregnancy is often raised, since treatment, unfortunately, will not bring positive results.
There are many factors that directly or indirectly influence the development of oligohydramnios during pregnancy. Let's list the most likely ones:
Oligohydramnios does not manifest itself to such an extent that the pregnant woman immediately suspects something is wrong - the clinical picture of the deviation in this case is blurred. With severe oligohydramnios, a woman may suffer from weakness, dry mouth, and frequent nausea. Sometimes the expectant mother feels pain in the lower abdomen, which intensifies when the baby moves.
During a diagnostic examination of a pregnant woman with oligohydramnios, the doctor will certainly note that the patient’s uterus is too small for the current stage of pregnancy, and fetal movements are significantly constrained. Ultrasound is used to confirm the diagnosis.
Correction of oligohydramnios begins with assessing test results - only in this way can a doctor determine the cause of the incident, determine the degree of the disease and the condition of the child. Only then can a treatment plan be developed.
If pregnancy occurs against the background of obesity and impaired metabolism in a woman, she is prescribed a special gentle diet, a healthier diet, vitamin therapy and medications that stimulate the blood supply to the membranes of the placenta. Moderate polyhydramnios can be treated on an outpatient basis; therapy for severe pathology is carried out exclusively in an inpatient setting.
Regardless of the severity of the disease, physical activity and physical activity are kept to a minimum; in most cases, the woman is prescribed bed rest. During the period of treatment for oligohydramnios, the expectant mother will more often undergo ultrasound and Doppler ultrasound - these procedures will help to notice in time unwanted metamorphoses in the body of the mother and her child. When, as a result of an ultrasound examination, it turns out that at 33 weeks (and later) the AFI indicators are too low, and meanwhile the baby is already ready to be born, the doctor will most likely decide on an early birth.
With polyhydramnios, AFI values are significantly elevated. About 1% of pregnant women face this problem when there is more amniotic fluid than necessary. The deviation can only be detected using ultrasound. Statistics say that a third of 1% of pregnancies end in miscarriage.
Doctors find it difficult to say exactly what underlies the pathology, but they still identified the main risk groups. Here are the diseases in which there is a high likelihood of developing polyhydramnios:
Depending on the speed of development, polyhydramnios can be acute or chronic.
The acute form of the deviation develops very quickly - literally within a few hours. This is a very serious problem, since its consequences are irreversible: the fetus either dies in the second trimester of pregnancy or survives, but is born with severe developmental abnormalities.
The chronic form of polyhydramnios does not develop immediately, so with timely diagnosis, doctors have time to intervene in this process and save the child. Often the deviation does not make itself felt in any way, and the expectant mother needs to monitor her well-being very carefully so that at the slightest suspicious symptoms she can go to the hospital with the problem.
The development of pathology can be suspected based on the following signs:
Only a timely reaction to what is happening and competent treatment will help a woman carry her baby to term.
The pathological condition can threaten the pregnant woman and her child with the following problems:
For a child, the consequences of polyhydramnios are no less dangerous. Here's what can happen due to this pathology:
To improve the condition of the expectant mother with polyhydramnios, doctors will first of all carry out a comprehensive examination of her - it is necessary to establish and eliminate the cause of the incident.
In parallel with the main course of treatment, the patient is prescribed a multivitamin preparation with the obligatory vitamins C, E and the B group of vitamins in its composition, preparations containing magnesium, diuretic drugs and, possibly, some kind of broad-spectrum antibacterial drug. Usually, with chronic polyhydramnios, the child can be saved.
Every woman who is preparing to become a mother should at least have a general idea of what the amniotic index means during pregnancy. Often it is precisely this lack of awareness that prevents pregnant women from understanding how important it is to be alert while expecting a baby. You cannot ignore even minimal suspicious symptoms in your health, because behind them there may be a serious illness that threatens the well-being of mother and baby. With the help of modern diagnostic procedures, doctors have a chance to detect and eliminate the problem in time, and determining and assessing the amniotic fluid index during pregnancy is one of them.
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