Twin Zygosity

Twin Zygosity

  • Legal testing for twins £425
  • Peace of Mind £270

Twin Zygosity tests help twin siblings confirm whether they are identical or fraternal. A doctor can often determine whether twins are identical or fraternal by examining the placenta(s) at birth:

  • Identical twins generally share a placenta
  • Fraternal twins typically have two separate placentas

However, if the placentas were discarded or damaged before twin zygosity was determined, or if the twins’ physical characteristics raise questions about their zygosity, a twin zygosity DNA test can provide the definitive answers a family needs. By comparing the DNA profiles of twin siblings, we can conclusively determine whether they are identical or fraternal. Identical twins will have matching DNA profiles, while fraternal twins will not.

Identical twins have matching DNA profiles because they are the product of one zygote (one egg cell that was fertilised by one sperm cell) that split during its early development. In contrast, fraternal twins do not have matching DNA profiles; their genetic profiles will look like those of any two non-twin siblings. This is because fraternal twins are the product of two zygotes (two egg cells that were fertilised by two sperm cells).