Zygosity testing

How can twins be sure of their zygosity i.e. whether they are identical or fraternal twins?

Research has shown that up to one-third of twins may be misinformed or unsure about their zygosity. Learn about why this occurs and why it is important to know your zygosity here

  • If you have a boy and a girl it’s easy, they will be non-identical or dizygotic (with very rare exceptions)
  • If they are of the same sex and definitely* shared one placenta, they are most likely identical or monozygotic. *Please note, for approximately 40% of non-identical twins, placentas fuse in the womb, so they may appear as one.
  • If they are of the same sex and each had a placenta, or if there is doubt about the type of placenta, then they could be either identical (monozygotic) or fraternal (dizygotic)

The best way to be certain is to do a zygosity test.

Discounted zygosity testing for TRA members

An Australian organisation, Identilab, provides a special discounted zygosity testing rate exclusive to members of Twins Research Australia.

The test is via a cheek swab from both twins (or all triplets). Your test kit is posted to you. You’ll receive your results via email within 5 business days of Identilab receiving your samples.

Identilab’s usual rate is $179. They offer TRA members a $45 discount, meaning you’ll pay $134 + postage. If you’re not already a member, learn how to join us. Membership is free.

To request a zygosity test and obtain the special $134 rate (per twin pair):

  1. If you are a TRA member, contact us on info@twins.org.au to obtain the unique discount code. If you have just joined TRA, your unique code will be in your welcome email.
  2. Go to the Identilab site here: https://identilab.com.au/product/twin-triplet-dna-test/
  3. Click ‘Order your DNA test today’ and complete the online order form*
    1. Complete all personal and order details and click ‘Place your order’
    2. At the top of the billing details page, make sure to enter your discount code (coupon) provided by TRA.

*We encourage you to read Identilab’s Terms and Service before placing your order with them. Don’t hesitate to contact them if you have any questions.