Abnormalities of the amnion and amniotic fluid

During pregnancy, the fetus is surrounded by amniotic membranes – chorion and amnion . The amnion forms a sac filled with amniotic fluid. It is produced by the epithelial cells of the amnion and is constantly exchanged (every 3 hours). Part of it is the urine secreted by the kidneys of the fetus. The amount of amniotic fluid increases up to 35-38 weeks of gestation (1-1.5 liters), after which it decreases and at term birth it is around 800-900 ml. In a transferred pregnancy, the volume of amniotic fluid decreases even more.

The functions of the amniotic fluid are:
– providing an environment with appropriate pressure and temperature for the movement and development of the fetus;
– protective function – the role of a buffer protecting the fetus and the umbilical cord;
– facilitates childbirth – helps to maintain pressure, protects the placenta, supports the maturation of the cervix (its smoothing and expansion).

In some cases, the amount of amniotic fluid is increased ( polyhydramnios ), and in others it is reduced ( oligohydramnios ), which can lead to disruption of its functions and various complications.

Polyhydramnios (polyhydramnios)

In Latin: Polyhydramnion
In English: Polyhydramnios

Polyhydramnios is an amount of amniotic fluid during term more than 1.5 L.

Epidemiological data:  The condition is detected in 0.2-1.6% of pregnancies.

Etiopathogenesis:  Increased production or decreased resorption of amniotic fluid can lead to hydramnios. The cause may be due to a disease of the mother, the fetus or the placenta. Factors associated with polyhydramnios are:
– diabetes of the mother (blood sugar of the fetus increases, and hence – the amount of urine excreted, which increases the volume of amniotic fluid);
– Rh-isoimmunization (due to Rh-incompatibility between mother and fetus);
– sometimes in multiple pregnancies in identical twins and the presence of one chorion (one placenta) and two amniotic sacs. The condition is referred to as feto-fetal transfusion syndrome – due to the presence of vascular anastomoses, one twin receives more blood and the other less, resulting in polyhydramnios in one amniotic sac and oligohydramnios in the other;
– intrauterine infections;
– on the part of the fetus – anomalies of the gastrointestinal tract with disruption of its patency – atresia of the esophagus, duodenum, diaphragmatic hernia, anomalies of the central nervous system, achondroplasia, chromosomal anomalies, etc.

Clinical picture: 

Rapid development of the condition is possible – acute hydramnios, and gradually – chronic hydramnios. The uterus has an increased size and volume during pregnancy and presses on neighboring organs and structures:
– the diaphragm is high, it is difficult to expand the lungs and there is shortness of breath;
– the heart is pressed, there is tachycardia;
– from the side of the gastro-intestinal tract – nausea, vomiting, difficulty in defecation;
– when blood and lymphatic vessels are pressed – swelling.

Complications:  Include:
– premature birth;
– prolapse of the umbilical cord (falling out of the umbilical cord before the fetus, which leads to its compression and risk of asphyxia);
– detachment of the placenta;
– complications from the cause of hydramnios – diabetes, fetal abnormalities, etc.

Diagnosis:  The diagnosis is based on:
– history of diabetes mellitus, diabetes insipidus, etc., symptoms such as shortness of breath, palpitations, swelling.
– physical examination – the uterus is larger for the duration of the pregnancy, the fetus is very mobile and difficult to palpate, it is difficult to hear the children’s heart sounds.
– testing for Rh-incompatibility between the mother and the fetus.
– ultrasound examination – determination of the amount of amniotic fluid, examination of the fetus.
– examination for congenital infections.
– karyotyping of the fetus (chromosome analysis).

Differential diagnosis:  It is done with:
– multiple pregnancy;
– ascites;
– ovarian cyst, etc.

Management:  Treatment for hydramnios is determined by the cause and the stage of pregnancy.
– With slightly increased amniotic fluid and no symptoms, the behavior is expectant.
– If symptoms are present – hospitalization. A therapeutic amniocentesis – draining of amniotic fluid – can be done. At the start of labor – bursting of the amniotic sac. The amniotic fluid should drain slowly to prevent prolapse (falling out) of the umbilical cord.

Oligohydramnios (hypohydramnios)

In Latin: Oligohydramnion
In English: Oligohydramnios

Oligohydramnios is a condition in which the amount of amniotic fluid is less than 500 ml.

Epidemiological data:  Malhydration has a lower frequency than polyhydramnios – 0.3-0.4%.

Etiopathogenesis:  Hypohydration is caused by:

  1. Primary:
    – with abnormalities of the urinary-excretory system of the fetus – lack of kidneys, renal polycystosis, impaired permeability of the excretory organs;
    – insufficiency of placental circulation – preeclampsia, dehydration, transferred pregnancy, etc.
    – in multiple pregnancy – feto-fetal transfusion syndrome;
    – use of ACE inhibitors.
  2. Secondary – when the amniotic sac ruptures.

Clinical picture: 

Symptoms usually appear as the pregnancy progresses. The pregnant woman may feel discomfort and pain during the child’s movements. In the presence of fetal distress (fetal distress), it may indicate a weakening of the baby’s movements.

Clinical symptoms include smaller uterine size and less amniotic fluid as detected by ultrasound.

Complications:  Complications in hypohydramnios are related to:
– impaired growth and development of the fetus – presence of anomalies, hypoplasia of the lungs, deformations of the musculoskeletal system, etc.
– squeezing the umbilical cord – suffering until the death of the fetus.
– difficulty in giving birth – severe pain, longer duration, birth trauma.

Diagnosis:  The diagnosis includes:
– history
– physical examination – the uterus is smaller for the duration of the pregnancy;
– ultrasound examination – reduced amount of amniotic fluid.

Behavior:  The behavior is determined according to the period of pregnancy, the condition of the fetus and the mother:
– to increase the volume of amniotic fluid – bed rest, hydration of the pregnant woman, if indicated – amnioinfusion.
– at discretion – induction (causing) of labor;
– when the amniotic sac ruptures – medical acceleration of the ripening of the cervix.


Abbas Jahangir

I am a researcher and writer with a background in food and nutritional science. I am the founder of Foodstrend.com, our reputable online platform offering scientifically-backed articles on health, food, nutrition, kitchen tips, recipes, diet, and fitness. With a commitment to providing accurate and reliable information, we strive to empower our readers to make informed decisions about their health and lifestyle choices. Join us on Foodstrend.com's journey toward a healthier and happier lifestyle.

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