Did you know the sac around the baby is made up of two layers, the amnion and chorion

Did you know the sac around the baby is made up of two layers, the amnion and chorion.

The amnion is the inner most layer that surrounds the baby, and the chorion is the outer layer. The chorion contains lots of small projections called villi, which act as the border between maternal and fetal blood during pregnancy.

These membranes are quite tough, and it takes quite a bit of pressure for them both to rupture. Some will rupture just before labour begins but the majority rupture spontaneously during established labour due to the pressure of contractions. Sometimes they are so strong that they don't rupture at all and the baby is born within the sacs.

In twin pregnancies the membranes surround the babies in different ways:

some babies share both an amnion and chorion (Monochorionic Monoamniotic or MoMo- identical). This is the rarer type of twins.

Some will have separate amnions and chorion (Dichorionic Diamniotic or DiDi - usually non-identical)

Some will have separate amnions but share a chorion (Monochorionic Diamniotic or MoDi - usually identical)

Fascinating right?

After birth, the placenta and membranes are checked carefully to ensure they are intact and that no remnants are left within the uterus.

Image @alydouli

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