Amniotic fluid index: weekly rate

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

The process of fetal development takes place inside a special fluid that serves as a whole world for a growing organism. Therefore, it is extremely important that the condition and quantity of waters be within the normal range. A pregnant woman can influence this by following the doctor's instructions, and also if she prepared for it in advance. Even if we exclude the risk of infectious and exacerbation of chronic diseases, most complications can be avoided.

What is IAI?

One of the important indicators that is monitored during an ultrasound examination is the amniotic fluid index. This is a special fluid that fills the entire space inside the placenta, is produced by the amniotic membrane and serves as a favorable environment for the development and protection of the fetus from external factors.

In everyday life there is a more familiar name - amniotic fluid, which is involved in the process of forming the child's immunity. The quantity and quality of water can tellhow is the development process going, are there any abnormalities or diseases.

From the beginning of development and up to 24 weeks, the skin of the fetus absorbs some of the amniotic fluid, thereby taking part in metabolic processes. Starting from the 25th week, the skin becomes denser, which is an obstacle to the penetration of amniotic fluid. The index and indicators regarding the amount of amniotic fluid begin to track from the second trimester of pregnancy.

What is amniotic fluid made of?

Depending on the gestational age, the composition of the amniotic fluid undergoes changes. For the first trimester of pregnancy, it is close in composition to the mother's plasma, in color it is transparent in a small amount. At this stage, the mother's body saturates the growing embryo with nutrients, proteins, vitamins, carbohydrates, lipids, hormones, oxygen, etc.

The second trimester is due to the rapid growth of the fetus. The color and composition of the waters also undergo changes. They may acquire a yellowish tint, since the bladder is already actively secreting the waste products of the growing body of the fetus. In the third trimester, the composition of the waters may contain secretion products of the sebaceous glands, vellus hair, epithelial cells. Remarkably, the amniotic fluid is renewed every three hours.

Methods for determining the level of amniotic fluid

In order to determine whether the amniotic fluid index corresponds to the weeks of pregnancy, there isa certain table with which doctors are checked. One of the easiest ways to determine the composition, presence of suspensions and the amount of water is ultrasound. The specialist determines the total volume of amniotic fluid based on the size of the so-called pockets (areas free from amniotic fluid). These indicators are indicative and have a margin of error. Since accurate sensors for determining the amount of liquid have not yet been invented, in conclusion you can see the value “+/-”.

Closer to the date of delivery, they can perform an amnioscopy. The procedure consists in examining the lower part of the fetal bladder using a special device. Allows you to determine the color of amniotic fluid.

The most radical way to diagnose the composition and index of amniotic fluid is amniocentesis. It consists in piercing the fetal bladder and taking a sample of amniotic fluid. The need for this procedure is due to the identification of genetic abnormalities in the development of the fetus. It also allows you to determine the biochemical, cytological, immunological parameters, how close they are to normal.

Norms of amniotic fluid in a pregnant woman by week

At the beginning of pregnancy, the amniotic fluid index is very small. According to the norms, by the end of the first trimester it is only 60 ml. Since the intensity of growth and development of the fetus falls on the second trimester, the water content in this period increases at the same rate. From the 13th to the 16th week of pregnancy, approximately 25 ml per week is added. At the time of the second screening(17-19 weeks) the volume of amniotic fluid reaches about 500 ml.

Third trimester waters consist mainly of urine produced by the body of the fetus, which is excreted up to 450 ml per day. The norm of the amniotic fluid index by 38-1 weeks of pregnancy is about 1-1.5 liters. This value may change if there are pathologies or abnormalities in the development of the fetus.

Low water

If during the ultrasound examination during the second screening it is established that there is a deviation from the norm of the amniotic fluid index (less than 500 ml), then this may indicate oligohydramnios. Also, indicators are measured by pocket size (in cm) and compared with a special table.

The reason for the development of oligohydramnios can be an infection that develops in the fetus, or there is a pathology (for example, the absence of kidneys or malformations of their development). Due to hypoxia, the excretion of urine into the amniotic fluid may decrease, which also leads to a small amount of amniotic fluid.

The presence of chronic diseases in a pregnant woman can lead to oligohydramnios, for example:

• Diabetes mellitus.
• Diseases of the cardiovascular system.
• Past viral diseases, bacterial infections.

Also, placental insufficiency, late preeclampsia, deviations in the development of membranes can also affect oligohydramnios.

In the second trimester, the norm of the amniotic fluid index in cm is from 12 to 14.5. depending on the week of pregnancy, they may be slightlydiffer, but not more than by one. In the third trimester, the numbers decrease slightly, which is explained by the growth of the child, from 14.5 to 11 cm. Therefore, a deviation from these norms to a smaller side serves as a reason for diagnosing oligohydramnios.

What threatens oligohydramnios?

It is customary to distinguish between primary and secondary oligohydramnios. If in the first case the fetal membranes remain intact, then in the second case amniotic fluid leaks. If it is insignificant, then the pregnant woman may not pay attention and take them for natural discharge. However, you can use a rapid test that determines the leakage of amniotic fluid.

Insufficient amount of amniotic fluid leads to developmental delay and occurs in 40% of pregnant women diagnosed with oligohydramnios. If up to 28 weeks the amniotic fluid index strongly deviates from the norm, the cause is identified, and an examination is carried out. In the worst case, in the presence of malformations and genetic abnormalities, the question of terminating the pregnancy may arise.

Before childbirth and during the process itself, oligohydramnios can serve as an obstacle to the normal opening of the cervix. Since the baby is cramped and there is not enough fluid to keep him moving, the chance of breech presentation becomes higher.

Treatment of oligohydramnios

You can cope with oligohydramnios if the cause is diagnosed in time. In most cases, bed rest, a special diet, a vitamin course and medications are prescribed to helpstimulate the blood supply to the placenta and fetus.

In order to monitor the he alth of the mother and child, Doppler ultrasound and ultrasound will be additionally prescribed. If there are positive dynamics, it will be possible to return to a normal lifestyle and expect a due date.

Starting at 32 weeks (low amniotic fluid index), if therapy is not possible, a caesarean section can be performed.

Polyhydramnios

About 1% of women experience polyhydramnios during pregnancy. The likelihood of developing this pathology may be due to:

• Multiple pregnancy.
• Chromosomal abnormalities and developmental anomalies in the fetus.
• Infectious diseases (including TORCH and related to the genitourinary system).
• Diabetes mellitus at any stage.
• Anemia, severe toxicosis.
• Kidney disease.

When calculating the norms of the amniotic fluid index by weeks of pregnancy, doctors take into account averages and always leave the probability of deviations up or down. However, if the diagnosis is confirmed, as a rule, after additional ultrasound studies and other tests, then you should be wary.

Polyhydramnios can develop very quickly (acute stage), and then it is important to make a decision to continue the pregnancy as soon as possible, because. there is a high risk of fetal death. If polyhydramnios develops gradually, then it is customary to call it chronic. In this case, doctors can resist the worsening of the coursepregnancy.

Obvious signs that should alert a woman:

• Increase in the volume of the abdomen (more than 120 cm in girth).
• Swelling in the legs.
• Pain in the lower abdomen.
• High heart rate.
• The size of the uterus is larger than due to the gestational age.
• Shortness of breath, weakness, constipation.

Pathologies of fetal development in polyhydramnios

If alarming symptoms are left unattended, you can greatly harm yourself and your child. Therefore, doctors compare the data with the table of norms, which indicates the necessary correspondence of the amniotic fluid index by week in cm (centimeters). Among the critical deviations in the development of pregnancy can be observed:

• Premature birth, which is very dangerous for less than 32 weeks.
• Placental abruption and heavy bleeding.
• Lack of labor activity or its weak course.
• Fetoplacental insufficiency.

For a baby, an abundance of amniotic fluid can cause active movement and the risk of cord entanglement. If the entanglement is tight, then the child may suffer from hypoxia. With polyhydramnios, the risk of infection and the development of defects in the central nervous system and heart is much higher.

Treatment regimen

After conducting research and testing, the doctor may advise taking a course of vitamins, for example, containing magnesium, vitamins of groups B, C, E. If the cause is an infection, then diuretic, antibacterial drugs are prescribeddrugs.

During childbirth, the process of piercing the bladder is carried out very carefully so that the flowing water does not flow in a swift stream. After the end of childbirth, the woman in labor is prescribed drugs that stimulate the contractile function of the uterus.

Color of amniotic fluid

Using ultrasound, you can understand whether the amniotic fluid index is normal. The 31st week is the time when the color of amniotic fluid is also of great importance, special attention is paid to this indicator. So, if the water is yellow, then this may indicate an Rhesus conflict. In the third trimester, for example, closer to the date of birth, about the content of fetal waste products in the fluid. The red color of the amniotic fluid indicates internal bleeding.

If the water turns green, it may be due to the release of meconium, the original feces. If its particles enter the child's body, it can lead to intoxication. This occurs in women who prolong their pregnancy.

Clear water is a sign of a normal pregnancy. Slight turbidity and the presence of suspensions of natural origin are allowed.