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What is the amniotic sac?

The amniotic sac is a thin-walled pair of membranes that contains the fetus and amniotic fluid during pregnancy. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the chorion, contains the amnion and is part of the placenta. The amniotic sac has a capacity of 4 to 5 L at term. The wall of the sac extends from the margin of the placenta. The intact sac and its fluid provide for the equilibration of hydrostatic pressure within the uterus. During labor, the sac effects the uniform transmission of the force of uterine contractions to the cervix for dilation.

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
The amniotic sac is filled with fluid that is released when a baby is ready to be born.

Watch this video animation where Dr. Oz explains the purpose of the amniotic sac.



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