The fluid-filled sac that encloses and protects the baby in the womb. It breaks at the beginning of the birthing process and releases its fluid.

The sac or "bag of waters" filled with amniotic fluid in which the developing baby grows. The membranes which make up the sac may occasionally rupture naturally as labour begins, but usually remain intact until the end of the first stage of labour. The membranes may also be broken by a midwife or doctor to speed up labour.

The thin walled sac inside the uterus that surrounds the baby, amniotic fluid and the placenta during pregnancy. It has a capacity of about 4 to 5 liters at term. The wall of the sac is made up from the amnion, chorion and decidua, each of which are just a few cell layers thick, and which extends from the margin of the placenta. While each of the layers are in contact, they are not fused together. The sac serves to maintain the equilibration hydrostactic pressure withing the uterus during pregnancy. During labor the sac transmits uniform pressure of the uterine contractions to the cervix for dilation.

Also known as the Amniotic sac, which is filled with Amniotic fluid. The fetus lives in this fluid.

Sac filled with amniotic fluid in which the fetus grows, which may rupture naturally as labor begins or be punctured to speed up labor.

A lay person's term for the amniotic sac and amniotic fluid.

The amniotic sac, or the bag of fluid that surrounds the fetus.