Dizygotic twin pregnancy

Last revised by Dr Jeremy Jones on 20 Sep 2021

A dizygotic (DZ) twin pregnancy is a type of twin pregnancy where two separate ova are independently fertilised by two separate sperm resulting the two separate zygotes. These twins are also known as fraternal twins or non-identical twins. They may or may not be of the same gender. 

Dizygotic twins are the most common type of multifetal pregnancy, accounting for approximately 70%. There is significant racial variation in incidence. The overall incidence is increasing due to the use of in vitro fertilisation (IVF).

A dizygotic twin pregnancy always results in dichorionic diamniotic pregnancies. This feature alone cannot be used to distinguish dizygotic from monozygotic pregnancies as approximately 20% of monozygotic pregnancies will also be dichorionic diamniotic

Risk factors for dizygotic pregnancy:

  • in vitro fertilisation (IVF)
  • advanced maternal age
  • family history
  • ethnicity (e.g. Nigerian 3)

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