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Thank you for your interest in joining our wonderful volunteer community! 
If you’re aged 18 years and above, register using the adult twin registration form.
Twins under 18 years of age can be registered by a parent or guardian using the junior registration form. Membership is free!

Twins of any age can join us – from 0-100+ years old! They can be registered as soon as they are born (and up to 18 years old) by their parents. Adult twins (18+ year old) register themselves. It doesn’t matter if you are identical or non-identical, same-sex or opposite sex twins, well or have health conditions – all are welcome to join us. 

Find out more about becoming a TRA member here

You can easily update your contact details here 

When a new study begins, TRA emails invitations to members who might be eligible to participate so they can decide if they would like to be involved. You might get a study invitation within a few months however sometimes it can take a few years. You can check out your eligibility for our current studies

Information concerning TRA members is kept strictly confidential; personal details are NEVER given to researchers or any other party without the express permission and consent of the individual member. Learn more here

Please first check the information on this page where our currently recruiting studies are listed. If you still have a question, please email us

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 share one placenta it’s also easy, they are almost always identical or monozygotic. 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 identical (monozygotic) or fraternal (dizygotic). The best way to be certain is to do a simple pain-free zygosity test, using samples of DNA from the babies (such as swabs taken from the inside of their cheeks). 

An Australian organisation, EasyDNA, currently provides the most competitive discounted zygosity testing rate available, which is exclusive to members of Twins Research Australia. If you would like to access this after your babies are born and you have registered to become a TRA member, you can visit the TRA website page here to request your discount code before arranging the test through EasyDNA

Visit here

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Firstly, congratulations on this exciting news! We have free resources available about twin pregnancy and birth, and what to expect when your babies go home. Request access to the website via this link

Not necessarily as approximately a third of monozygotic (identical) twins each have their own placenta. Learn more here

While there has not been any research to show that identical twinning can be inherited, non-identical twinning can be. Learn more here

Twin-to-Twin Transfusion Syndrome (TTTS) affects approximately 15% of identical twins that share a placenta. The condition occurs when blood from one twin (commonly called “the donor”) is transfused into the other twin (commonly called “the recipient”) via blood vessels in the shared placenta. It can also occur in triplet or quadruplet pregnancies in which foetuses share a placenta. Learn more

See here for an explanation of the different terms.