Normal amniotic fluid index by week. Causes, diagnosis and treatment of oligohydramnios in pregnant women

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

The official medical name for amniotic fluid is amniotic fluid. It is a liquid biologically active medium that is in the fetal membranes and covers the embryo.

Functions of amniotic fluid

Amniotic fluid is one of the factors in ensuring the life of the child in the womb. This biological environment is characterized by several functions at once:

• Providing fetal nutrition. This liquid is made up of many nutrients. In the first period after fertilization, they are absorbed through the skin of the child, and a little later, the baby independently swallows a certain amount of them.
• Maintaining the appropriate pressure and temperature within 37 oC.
• Providing a developing child with protection from external mechanical influences. Amniotic fluid significantly reduces the pressure and shocks that come from the external environment.
• Support for sterility, which is to protect the child fromvarious infections. The amniotic fluid contains a lot of immunoglobulins. In addition, the absolute tightness of the fetal bladder plays an important role. Sterility is ensured by the constant renewal of amniotic fluid, which ends only after the birth of the child.
• Ensuring the free movement of the baby in the uterus.
• Mute strong ambient noise.

Main indicators of amniotic fluid

Throughout the duration of pregnancy, the composition and amount of amniotic fluid are very important. There are many cases when abnormal indicators indicate the formation and development of various pathologies. Thus, it is possible to diagnose and eliminate them in time, or to properly prepare for the necessary measures after the birth of the baby.

Amniotic fluid index (AFI) is a number that indicates its volume in the amniotic sac.

When diagnosing a specialist, the following indicators are taken into account:

• Hue and transparency. The usual color of the liquid is light, transparent, with a small amount of impurities.
• Volume. The amount of fluid is affected by gestational age. Therefore, the rate of amniotic fluid depends on the trimester of pregnancy. For example, the amniotic fluid index at 21 weeks (normal) is 88-143-233 ml, where the first indicator is the lower norm, and the second number is the average, the third is the upper limit. daily increasethe amount of fluid per 40-45 ml continues until 32 weeks of pregnancy. After the amniotic fluid index at 32 weeks (the average norm is 144 ml) has reached its peak, the amount of water gradually decreases. On the eve of childbirth, it is only 500-1500 ml.
• Hormonal content.
• Biochemical and cytological compositions.

Indicators of amniotic fluid

The most informative criterion for oligohydramnios in our time is ultrasound. When conducting this study, the doctor determines the AFI and the multiplicity of the vertical pocket. If these indicators do not reach the normal limits for a given gestational age, then oligohydramnios is indicated in the conclusion.

Vertical pocket is the name of the longest section of free amniotic fluid that is located between the fetus and the anterior abdominal wall. In addition, the location of the free fluid of the umbilical cord or the limbs of the child in this area is not allowed. The norm for the length of a vertical pocket is 5-8 cm, a little earlier, with the help of ultrasound, only this indicator was established.

Norms of amniotic fluid index

Now the amount of amniotic fluid is estimated using AFI. To do this, the doctor mentally divides the abdomen into 4 parts using 2 perpendicular lines intersecting at the navel. After that, in each of these zones, the measurement of the maximum vertical pocket is carried out. In order to get the final value of the amniotic fluid index, you need to add up all the obtained indicators.

The norms of the amniotic fluid index are calculated by weeks of pregnancy, starting from the 16th week. Their value is gradually increasing. The highest index of amniotic fluid at 32 weeks is the norm from 77 to 169 ml. This is followed by a decrease in AFI.

IAI norm table

Norms of the amniotic fluid index by week are presented in the table.

IZHA norm table

Lines of pregnancy (weeks)	Lower limit of normal	Average	Upper limit of normal
16	73	121	201
17	77	127	211
18	80	133	220
19	83	137	225
20	86	141	230
21	88	143	233
22	89	145	235
23	90	146	237
24	90	147	238
25	89	147	240
26	89	147	242
27	85	156	245
28	86	146	249
29	84	145	254
30	82	144	258
31	79	144	263
32	77	143	269
33	74	142	274
34	72	140	278
35	70	138	279
36	68	135	279
37	66	132	275
38	65	127	269
39	64	123	255
40	63	116	240
41	63	110	216
42	63	110	192

If these indicators do not correspond to specific lines of pregnancy, polyhydramnios or oligohydramnios occur.

Oliver pregnancy

Oligo is a rather unpleasant and very common occurrence during pregnancy. If the deviation of the amount of amniotic fluid from the norm of the amniotic fluid index for weeks is insignificant, a diagnosis of "moderate oligohydramnios" is made. In order to correct it, you can use a diet, proper nutrition and a he althy lifestyle. After a while, the amount of water returns to normal and does not affect the child's condition in any way.

The diagnosis of "pronounced oligohydramnios" is made in the case when the deviation from the norm of the indexamniotic fluid weekly down large. With such a diagnosis, urgent hospitalization and inpatient treatment are necessary. This is due to the high likelihood of dire consequences for the child.

If the amniotic fluid index at 20 weeks (normal) is in the range of 86-230 ml, and the ultrasound results indicate a much lower real volume of amniotic fluid, if left untreated, this can provoke underdevelopment of vital organs, deformation of the skeleton bone, development of various fetal pathologies. Therefore, it is very important to start the treatment of severe oligohydramnios in time.

When a low amniotic fluid index was determined at 34 weeks (the norm is an average of 142 ml), in addition, there are already well-defined deviations in the development of the child - the question often arises of terminating a pregnancy, since treatment in this case meaningless and will not bring any results.

Causes of oligohydramnios

There are many reasons for the formation of oligohydramnios. The main ones are:

• underdevelopment of membranes or reduced secretion of water;
• abnormal development of the fetus (its kidneys, skeleton);
• high blood pressure in the expectant mother, especially with significant deviations from the norm;
• bacterial infections that penetrate not only through the genital tract, but also directly into the amniotic fluid;

• multiple pregnancy, with uneven development of the placenta, givingdifferent blood flow to each fetus;
• overwearing;
• disturbed metabolism in a woman's body, especially if she is overweight.

Features of the treatment of oligohydramnios

Even moderate oligohydramnios cannot be treated on its own. Only on the basis of previously made tests, the doctor can assess the cause of the anomaly, the severity of the disease, the condition of the fetus and prescribe a course of treatment.

If there is obesity, impaired metabolism, it will be necessary to follow a diet, eat right, take vitamins and drugs that improve the blood supply to the placenta. Therapy of moderate polyhydramnios can be performed on an outpatient basis. A pronounced stage is treated only in a hospital. Regardless of the form of the disease, there is a need to limit physical activity and the amount of physical activity, adherence to bed rest.

During treatment, it will be necessary to do ultrasound and dopplerography more often than usual to timely determine changes in the bodies of the pregnant woman and the baby.

If the ultrasound results showed a low amniotic fluid index at 33 weeks (the norm is an average of 143 ml) or later, when the baby is ready to be born, the doctor may prescribe an early delivery.

When you discover this fact, do not get depressed. Still can be corrected - moderate stages are curable. In the presence of oligohydramnios during previous pregnancies, it is necessary to inform the doctor about this. In this case, he will be able todetect and fix this problem.