Mono mono twins, also known as monochorionic-monoamniotic (MoMo) twins, are identical twins that share both a single placenta and a single amniotic sac during pregnancy.
Definition
These twins develop from one fertilized egg that splits late, around 9-13 days after fertilization, after the amniotic sac forms. They are always monozygotic (identical) and represent the rarest type of twins.
Rarity
MoMo twins occur in about 1 in 10,000 pregnancies, or 0.01% of all twin pregnancies. This makes them far less common than other identical twin types like mono/di (sharing placenta but separate sacs).
Risks
The shared sac raises dangers like umbilical cord entanglement, which can restrict blood flow and oxygen to the babies. Pregnancies often require close monitoring and early delivery around 32-34 weeks.
