Monozygotic twin pregnancy

Dr Amir Rezaee and Radswiki et al.

A monozygotic (MZ) twin pregnancy results from division of single zygote following fertilisation and share similar genetic materials. These twins are therefore always of the same gender.

MZ twins account for approximately 30% of all twin pregnancies 1. The estimated incidence is at ~1 in 250 births with little racial variation for this sub type 3 (c.f dizygotic pregnancy).

Depending on the time of division of the zygote, there can be many possibilities

Prenatal diagnosis of chorionicity is important as monochorionic pregnancies have increased rates and severity of all types of obstetric complications when compared with dichorionic pregnancies. Monozygotic twins have higher rate of fetal anomalies although they tend to be discordant-only affecting one twin despite identical genetic makeup.

Monochorionic twin pregnancies share the one placenta and are therefore prone to haemodynamic complications such as:

Monochorionic monoamniotic twins also carry additional cord related complications such as:

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Article Information

rID: 14637
Tag: cases
Synonyms or Alternate Spellings:
  • Monozygotic twins
  • Identical twins
  • MZ twins

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