Dizygotic twin pregnancy

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. 

Epidemiology

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).

Embryology

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)

See also

• monozygotic twin pregnancy