More than you ever wanted to know about Monoamniotic twins

Monoamniotic twins are a rare type of identical twins that occurs in approximately 1% of identical twin pregnancies or somewhere between 1 in 35,000 and 1 in 60,000 pregnancies. It occurs when the "split" happens about 9 days after fertilization. Most identical twins split much earlier than this. If our twins had waited any longer to divide they might have been conjoined!

If the split occurs early, each baby will have its own placenta and own amniotic sac. A few days later and the placenta will have formed, but each baby will have its own amniotic sac. Around 9 days later like our girls - and they will be share both a placenta and amniotic sac. Basically they are already having to share a bedroom!

A monoamniotic twin pregnancy is quite high risk because their umbilical cords become entangled and can eventually get compressed. Most monoamniotic pregnancies do not go beyond 34 weeks (40 weeks being full term).