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This rare type of identical twins not only share a placenta, but also share the same amniotic sac (pocket of fluid). They carry a higher risk of complications, such as miscarriage, stillbirth, fetal anomalies than identical twins, but also have a risk of cord entanglement. Due to the small numbers of these twins, there is insufficient evidence to establish the best way to manage these twins, and that further research is required in this area.

At St George’s, we have collaborated with other centres to produce a larger sample of these twins, in order to analyse their outcomes, complications, as well as the best ways to manage these twins when they are further complicated by selective fetal growth restriction.

Prevalence, Antenatal Management and Perinatal Outcome of Monochorionic Monoamniotic Twin Pregnancy: A Collaborative Multicenter Study in England, 2000-2013

Weight Discordance and Perinatal Mortality in Monoamniotic Twin Pregnancy: Analysis of MONOMONO, NorSTAMP and STORK Multiple-Pregnancy Cohorts