The inner of two membranes that surrounds your baby in utero making up the amniotic sac. It makes up the outer most layer of the umbilical cord (definition link), it covers the foetal side of the placenta (definition link) and surrounds the foetus. The outer membrane is called the chorion (link to definition). Together these membranes provide an enclosed environment that act as a barrier to external infection, hold the amniotic fluid (definition link) and provide the space for your baby to grow and develop in. When you deliver your placenta (definition link) at birth, the Midwife will then check it. Part of that check is making sure that both the amnion and chorion are present and complete.