Amniotic Sac

The foetus develops in a fluid-filled space that is encased by an amniotic sac

  • The amniotic sac separates the foetus from the mother and hence functions as a barrier against infection

The amniotic sac is filled with a protective liquid called amniotic fluid, which serves a number of key roles:

  • The fluid is largely incompressible and good at absorbing pressure, and so protects the foetus from impacts to the uterus
  • The fluid also creates buoyancy so that the foetus does not have to support its own weight while a skeletal system develops
  • Finally, amniotic fluid prevents the dehydration of foetal tissues

The amniotic sac ruptures when a woman comes to term during labour – this is known as her ‘waters breaking'

Ultrasound of the Amniotic Sac

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