The membranes consist of two very thin structures called the amnion and the chorion. The membranes form the lining of the inner aspect of the uterus during pregnancy and they are responsible for forming the bag within which the water or amniotic fluid is contained. The most important duty of the membranes is to maintain and keep the amniotic fluid within the cavity of the uterus, because without the amniotic fluid a pregnancy cannot continue. If the membranes rupture the waters break and the amniotic fluid will drain away, which is a characteristic occurrence either at the onset of labour or at some stage during the process of labour.
The membranes are also known as the caul. David Copperfield was supposed to have been born in a complete caul, which used to be considered a good omen and an indication that the person would never drown at sea. Even today some people have a fear that a child may suffer adversely as a result of being born with the membranes unruptured. It is almost impossible for this to happen, but should it occur there is certainly no harm done to the baby since the membranes can be easily broken and removed from the baby’s face and mouth.