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Amniotic Sac

What Is The Amniotic Sac?

The amniotic sac is a bag of fluid inside the womb in the uterus. The amniotic sac is where the unborn baby develops and grows. 

It is also referred to the membranes because the sac is made of two layers called the amnion and the chorion.  The bag is thin transparent that holds the developing baby. 

Amniotic Sac Structure

After women get pregnant, the amniotic sacs start to form gradually preparing for the growing embryo. The two membranes that help form the amniotic sac are:

  • Chorion: The outermost membrane that surrounds the embryo between the developing fetus and mother. 
  • Amnion:  The innermost membrane that encloses the embryo.  

Function Of The Amniotic Sac

The amniotic sac, which contains amniotic fluid and helps the growing fetus. 

The functions of the amniotic sac it helps the baby stay warm, the fluid provides lubrication that helps the baby move and keeps them from growing together. 

 It also provides a safe place from any visible bumps or any pressure. 

Amniotic Sac In A Twin Pregnancy

A twin pregnancy each baby will have their own amniotic sac and umbilical cord. Having their separate amniotic sac helps them develop correctly and equally. 

The Amniotic Sac At The Time of Birth

When it's time for labor to start the amniotic sac breaks.  It is usually referred to the water breaking discharging the fluid through the vagina.  Make sure to seek medical attention right away when the water breaks. 

Caul Birth

A caul is a piece of membrane that can cover a newborn's head and face. Caul births are an extraordinarily rare event. 

Artificial rupture of the membrane (Amniotomy)

The surgical procedure that helps manually ruptures the amniotic membrane is referred to artificial rupture of the membranes.

Complications Associated With The Amniotic Sac


  • Premature rupture of membranes (PROM)
  • Blighted ovum
  • Amniotic sac prolapse
  • Chorioamniotic separation

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