What is the fluid filled sac that protects the baby until birth?

The mother's womb is filled with amniotic fluid which surrounds the fetus. This amniotic fluid is filled in a sac like covering made up of two layers known as amnion and chorion. The fetus grows and develop inside the amniotic fluid filled in the sac. The sac filled with the amniotic fluid surrounding the fetus is known as the amniotic sac.