Your baby is growing inside your uterus or womb within a bag of fluid. This bag of fluid is called the amniotic sac. You may hear the amniotic sac also referred to as the membranes. This is because the walls are made up of two membranes known as the chorion and the amnion. The membranes keep your baby sealed inside the amniotic sac and surrounded by the amniotic fluid. These membranes usually break apart during labour to release the fluid ready for birth. This is known as your waters breaking.
Inside the amniotic sac is a liquid which is clear and pale straw-coloured. This liquid is known as amniotic fluid although it is mainly water. Your baby is cushioned inside the amniotic sac by the amniotic fluid which allows your baby to move and prevents injury from any bumps. The amniotic fluid also keeps your baby at the correct temperature, protects the baby from infections and allows your baby’s lungs and digestive system to mature ready for birth.
A few days after your baby is conceived, the amniotic sac begins to form and begins to fill with amniotic fluid. As your baby grows, he will begin to pass small amounts of urine into the water from about 10 weeks.
by Jenny, mum to William and James