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What is amniotic fluid?
Nourished by the placenta, the fetus floats in the amniotic liquid. This liquid, essentially composed of water, protects it and promotes its development in utero. Amniotic fluid is produced from the formation of the amnion (the envelope that is formed around the embryo), that is to say from the first weeks of pregnancy. Until the 4th month, it is secreted by transudation, through the fetal skin and amniotic membranes. After 20 weeks, the fetus begins to keratinize. His skin no longer allows water to pass freely. The kidneys will take over. Now able to function, they will secrete small amounts of urine.
Throughout pregnancy, the amniotic fluid will mainly be formed by the baby’s urine and secretions from the lungs. Perpetually renewed, the baby swallows the amniotic fluid, swallows it and eliminates it while urinating. It absorbs between 200 and 500 ml per day. Its volume increases gradually to reach an average of 600 ml at the end of pregnancy. The amniotic fluid flows normally during childbirth: this is called the rupture of the water bag, or loss of water.
What is the role of amniotic fluid?
It has a protective role at different levels. This clear, limpid liquid can be compared to a soft pillow that surrounds the baby. It thus protects it from external shocks, from the cold, keeping it at a temperature of 37,5 degrees. The water allows the active movements of the fetus essential for the development of its motor skills in the womb of its mother. It also promotes the development of its senses in terms of taste, smell and hearing. But above all he has a powerful antibacterial role. Most infections do not pass through the placenta. Except in certain extreme situations, when the mother is, for example, infected with toxoplasmosis or cytomegalovirus (CMV).
What if there is too much or too little amniotic fluid?
During the ultrasound, the doctor assesses the volume of amniotic fluid. This subjective impression allows him to tell whether everything is apparently normal. If he has any suspicion, he may decide to measure its quantity with the amniotic index. Note that all women have roughly the same amount of amniotic fluid. In the event of anomalies, there are several explanations.
- If the amniotic fluid is too abundant: hydramnios
The first cause is the mother’s diabetes. But sometimes the origin is infectious. Too much amniotic fluid, called hydramnios, can also be a telltale sign of fetal malformations. The baby’s intestine is blocked, there is a problem with the esophagus that does not communicate with the stomach. The baby therefore cannot swallow. And the liquid accumulates in the water bag. The risk is premature delivery. Too much fluid can stretch the uterus, causing contractions, and therefore alter the cervix.
- If the amniotic fluid is insufficient, oligoamnios
In this case we speak ofoligoamnios, which generally corresponds to a rupture of the water bag. At the beginning of the third trimester, the loss of water is not very serious, although germs can rise and therefore infect the baby. It is more problematic at the start of pregnancy. Beyond the risk of infection, the baby can move less well, he may not develop normally.