Baby’s head popping out with the amniotic membranes still intact during a cesarean section delivery ! ! This fluid-filled sac cushions the fetus , protects the fetus from damage and allows the fetus to move freely . In most cases , rupture of the amniotic sac occurs spontaneously at full term either during or at the beginning of labor . This process is better known as " water breaking " , although in rar . . .