Amniotic fluid is a sterile, clear, watery liquid which bathes the embryo and then the foetus throughout pregnancy in mammals. The very great majority of amniotic fluid is water (97%). It also contains foetal cells and foetal urine.
Role of amniotic fluid
Amniotic fluid allows the gestating baby to move around without risks, protects it from knocks and external noise and allows it to develop in an environment at body temperature. The mother's organs are also protected from knocks from the foetus.
It is continuously secreted and removed The foetus swallows it and in this way activates its kidneys.
Around the 34th week of pregnancy in the woman, the amniotic fluid reaches its maximum volume of approximately 1 litre.
Slightly before childbirth, when the uterus contracts, the water sac breaks. The fluid then pours out and lubricates the birth canal to facilitate the imminent delivery of the baby.
Diseases of amniotic fluid
There are two pathological situations involving amniotic fluid:
- Oligohydramnios, which is a lack of amniotic fluid (< 200 mL). There is nothing to worry about this if it is transient. If it continues longer term, however, the risks become greater. Generally, the water sack ruptures;
- polyhydramnios which is an excess of amniotic fluid (> 2 L). This increases the likelihood of uterine contractions which may rupture the water sac. If this occurs too early in a pregnancy there is a risk of premature birth.
A pregnant woman does not only carry the additional weight of the baby. She also needs to carry 1 kg of amniotic fluid. © Maxime Delrue, cc by nc nd 2.0