Lecture of amniotic fluid (low amniotic fluid)

2021-03-22 12:00 AM

Major nervous system abnormalities, which may be related to normal amniotic fluid intake, and increased amniotic fluid intake.


Low amniotic fluid (or oligohydramnios) is when the amount of amniotic fluid decreases compared with the normal amount of amniotic fluid for gestational age and is below the 5th percentile line.

The rate of amniotic fluid is about 0.4 - 3.9%.

The causes of minimal amniotic fluid include premature rupture of the amniotic fluid, premature rupture of the fetus, fetal structural abnormalities, fetal overdue, poor fetal development in the uterus ... However, there are many cases of minimal amniotic fluid be the cause.

The amniotic fluid that occurs in the early stages of pregnancy usually has a poor prognosis, while the amniotic fluid in the fetus beyond the date of birth usually has a better prognosis.

Small amniotic fluid carries the risk of compression of the umbilical cord and leading to fetal failure, which increases during labor.

Causes of minimal amniotic fluid 

The reason is the mother

Maternal pathology affects the permeability of the amniotic fluid and the function of the placenta, causing poor fetal development and amniotic fluid regeneration function such as high blood pressure, pre-eclampsia, liver and kidney disease ...

Causes of pregnancy

At all stages of pregnancy, the most common cause of amniotic fluid is premature rupture of membranes. There are often some congenital abnormalities of pregnancy with amniotic fluid. Common fetal abnormalities associated with amniotic fluid are:

Nerve system:

Although major nervous system abnormalities may be related to normal amniotic fluid intake and increased amniotic fluid intake, only in limited cases amniotic fluid is related.

Intracranial pregnancy.


Meningeal hernia.

Digestive system:

Rarely, often a blockage of the digestive tract is the cause of poly amniotic fluid.

Umbilical hernia.

Detect the oesophagus - trachea.

Duodenal atrophy.

Respiratory system:

Pulmonary dysplasia.

Urinary system:

Urinary tract obstruction or no kidneys. The most common diseases are renal aplasia, renal paresis, and polycystic kidney.

Amniocentesis in utero developmental delay occurs following a state of fetal hypoxia, decreased pulmonary perfusion, and decreased secretion.

Pregnancy infection can also be a cause of amniotic fluid. Some Prostaglandin resistance or cancer chemotherapy can cause amniotic fluid.

In about 30% of cases, no cause is found.

Usually, there is an angiotensin-converting enzyme inhibitor of amniotic fluid.

Symptoms and diagnosis

Uterine height is usually smaller than the apparent gestational age, measurements are usually low and tend to go down compared to the calibration curve.

The fetus often moves weakly. When performing the 4 procedures of Leopol, we can clearly see the fetal parts lying close to the hand without feeling amniotic fluid, making it difficult to move the fetal head.

Ultrasound has a low amniotic fluid index, usually below the 5th percentile for gestational age or when gestational age after 35 weeks has an amniotic fluid index (AFI) ≤5 or is the largest amniotic fluid at depth ≤ 2.


It is necessary to make a differential diagnosis of premature rupture of membranes. So far, there is no effective treatment and prevention of amniotic fluid. Therefore, it is advisable to advise pregnant women to have regular antenatal check-ups, to do tests to detect the mother's diseases and fetal abnormalities in order to have timely treatment and careful monitoring.

Ultrasound is a routine test to evaluate the amount of amniotic fluid and detect fetal malformations, and examine the uterine - vegetable and fetal circulation doppler to evaluate the fetal status. Cases when having minimal amniotic fluid must carefully examine the fetal urinary system morphology and function.

On ultrasound, if the largest amniotic fluid is <10 mm and the amniotic fluid index AFI <5 is sure to have minimal amniotic fluid. If the AFI is between 5 and 24 amniotic fluid manifestations within the normal range.

Small amniotic fluid almost does not cause complications for the mother, the problem of treatment changes depending on the condition of the fetus.

The fetus is not yet full term

If amniotic fluid without major congenital malformations in the urinary organs, digestive tract, nerves ... may be due to failure or partial obstruction of uterine circulation - placenta. So far, there is no known specific treatment. In these cases, it is advisable to advise the patient to lie on her left side, control comorbidities, ensure adequate nutrition to improve uterine circulation - placenta in order to try to keep the fetus growing to over 35 weeks.

In cases of amniotic fluid and fetal structural defects, additional tests are needed to determine if the abnormality is treatable, as well as whether there is a chromosomal abnormality There is a decision to treat pregnancy or suspend a pregnancy. In case of fetal development delay in the uterus without finding a cause, the attitude of management depends on the progression of the fetal failure in the uterus. Late fetal growth in the uterus in the third trimester and lack of amniotic fluid is a sign of fetal growth retardation. Consideration should be given to the possibility of terminating a pregnancy in the presence of fetal impairment and/or an adult fetal lung.

The fetus is at full term

When determining the term pregnancy and symptoms of amniotic fluid, it should be monitored by monitoring. If there is no slow fetal heart rate or variable dip in the fetal heart when not doing a shelling test or while doing a shelling test, it is necessary to appoint a cesarean section to end the pregnancy. If a prick test is done but the fetal heart rate remains within the normal range, it is necessary to further evaluate the Bishop's index for indication of induction of labor.

During labor

Small amniotic fluid increases the risk of fetal failure and difficult delivery because umbilical cord compression and the fetus are difficult to correct well in labor, so it is necessary to closely monitor labor factors for prognosis and timely management.


The prognosis of pregnancy is often poor with high mortality with minimal amniotic fluid in early pregnancy. On the other hand, a fetus (undergoing prolonged amniocentesis, regardless of the cause) can have minimal amniotic effects such as pulmonary dysplasia, facial and bone malformations (hip dysplasia, amputation, scoliosis, and other Other defects in limbs).

Amniotic fluid usually causes pulmonary dysplasia because of the following 3 reasons:

Due to the compression in the chest, the movement of the lungs is reduced.

Reduce fetal breathing movements.

Due to underdeveloped lungs.