Synonymous that labor has started, the loss of water is the signal to leave for the maternity ward. How to recognize it? What if it occurs prematurely? We tell you everything.

The amniotic cavity is where the baby lives for nine months. Its wall is made up of an internal membrane, the amnion, and an external membrane, the chorion. This pocket is filled with amniotic fluid, a clear, watery liquid composed of 96,4% water (1) and other substances (mineral salts, secretions from the mother and the fetus, enzymes, hormones, etc.).

From the fourth month, the fetus is completely surrounded by amniotic fluid which performs different functions:

• a mechanical role: it absorbs shocks, protects the baby from noise, ensures a constant temperature, prevents compression of the cord, allows the fetus to move freely, thus allowing it to grow well and develop its lungs thanks to regular respiratory movements .
• an antibacterial role: sterile, the amniotic fluid protects the fetus from germs that can rise from the vagina.
• a nutritional role: it provides water and mineral salts to the fetus which continuously absorbs this liquid via the mouth and the skin.

At the end of pregnancy, the accumulation of liquid in the lower part of the uterus forms the “water bag” which, by pressing on the cervix, will promote its dilation.

The spontaneous rupture of the water bag, or “water loss” in everyday language, corresponds to the rupture of the membranes (chorion and amnion) at the end of pregnancy. It results in the loss in greater or lesser quantity of a transparent, hot and odorless liquid comparable to water. It can occur without even uterine contractions. However, it gives the signal to immediately leave the maternity ward because once the pouch is ruptured, the baby is no longer protected from the germs which can rise from the vagina. Without this protection, the umbilical cord also risks being pulled down and compressed (cord procidence). If after the rupture of the water bag, labor still does not start, triggering may be considered.

The rupture of membranes is said to be premature when it occurs before the onset of labor.

However, there are two situations:

• premature rupture before 37 weeks or “before term”. It concerns 3% of pregnancies (2), and involves a risk of infection and a risk of prematurity.
• premature rupture at term affects 8% of pregnancies (3). After 37 weeks, the risk of prematurity no longer exists.

Depending on the term, the management of premature rupture of membranes will therefore be different:

• in the event of premature rupture of the membranes at term, triggering is often carried out in order to limit the risk of infection. More rarely, antibiotic therapy is given while waiting for labor to start spontaneously.
• in the event of premature rupture of the membranes before term, a clinical assessment (to look for an infection) and fetal are carried out. If they show chorioamnionitis and / or fetal distress, the child should be delivered either by induction of labor or by cesarean section.

Amniotomy consists of breaking the membranes (or water bag) during labor using a long instrument with a perforating end inserted through the opening of the uteÌ ?? rin neck. It is a frequent gesture. carried out in order to speed up the work. It allows the baby’s head to press directly on the cervix, and therefore to facilitate its dilation. The rupture of the water bag also causes the release of arachidonic acid and the synthesis of prostaglandins, two substances that stimulate contractions. This is why after the amniotomy, the pregnant woman perceives the contractions in a more intense and painful way.

According to detractors of amniotonia, however, the water bag and amniotic fluid play an active role in protecting the fetus from uterine contractions, in facilitating cervical changes and in allowing the perineum to be stretched beforehand. The pressure exerted by the membranes on the uterus would also stimulate oxytocin spikes, necessary for contractions (4). A meta-analysis (5) of 14 randomized controlled trials found no statistically significant reduction in the duration of the first stage of labor.