As a leading provider of peace of mind DNA testing for members of the public, we are often asked about the science behind DNA testing, especially when we’re talking about twins.

In Ireland, around 2% of pregnancies result in twins.

A rise in the number of people having fertility treatments, such as IVF, also means that multiple pregnancies are becoming more common, while women with twins in their extended family are more likely to have twins themselves.

In this article, we look at the science behind twin DNA (zygosity) testing, how the test is performed, and when you might want to order a Twin DNA Test.

What is a twin DNA test?

A twin DNA test – also called a zygosity test – is a DNA test that can be used to determine whether multiple children from the same birth (twins, triplets, quadruplets etc.) are identical or non-identical.

If siblings are identical, they are known as monozygotic. This means that they were formed from a single fertilised egg, which went on to split into separate embryos.

Monozygotic (identical) twins share the same DNA profile, physical features, and sex (gender).

If siblings (twins) are non-identical, this is known as dizygotic (i.e. having two zygotes) or fraternal twins.

This means that these siblings are the result of separate fertilised eggs and, although they do not have the same DNA profile, they will share DNA in common (as is the case for siblings from different births).

How is a twin DNA test performed?

An AlphaBiolabs Twin DNA Test (zygosity test) is performed using the very latest technology and techniques in DNA analysis, to determine whether siblings from multiple births are identical or non-identical.

The test requires a cheek (buccal) swab to be rubbed quickly and painlessly on the inside of each sibling’s cheek to collect cheek cell DNA. This simple, non-invasive method of sample collection can be done at home.

Once the DNA samples arrive at the laboratory, expert geneticists compare both samples, analysing up to 42 DNA markers (loci) to identify matching DNA markers.

If the siblings are identical (monozygotic) they will share the same DNA profile. If they are non-identical (dizygotic or fraternal twins), they will have different DNA profiles, but they will still share DNA in common, like siblings from different births.

Once we have completed the Twin DNA Test, a zygosity certificate is issued confirming the results. This can make a unique gift for multiple birth parents, who want to confirm whether their children are identical or non-identical.

When is a twin DNA test useful?

There are many reasons why you might want to order a Twin DNA Test.

Examples include:

  • It wasn’t clear during pregnancy (in utero) whether the twins were identical or non-identical. Identical twins do not always share the same placenta and sac – it all depends on when the egg splits
  • You want to assess the likelihood of conceiving twins again
  • One sibling has been affected by an illness, and you want to know whether you need to test the other sibling for the same condition
  • You need the information to take part in a study about multiple births
  • You want to buy a Twin DNA Test as a gift for multiple birth parents or their children

Knowing whether twins are identical or non-identical can also be useful for reinforcing the need to treat siblings as individuals.

Where can I buy a twin DNA test?

It’s easy to buy an AlphaBiolabs Twin DNA Test online now from our award-winning, ISO 17025-accredited laboratory.

For just €139 you’ll receive your secure, password-protected results via email the next day (included in the cost of your test) or the same day for an extra €50.

Here’s what AlphaBiolabs customer, Kelly Coupland, said about our Twin DNA Test:

“After receiving a lot of comments that our twin girls look very similar, we ordered the Twin DNA Test (Zygosity Test) from AlphaBiolabs. They are DCDA twins (have separate sacs and placentas) and twins also run in the family so as much as I really wanted identical twins, I thought they’d be non-identical. 

“The test kit arrived quickly, and it was really easy to conduct (even with my twins being premature in NICU). I was so impressed that I could receive the results on the same day the lab received the swabs back.

“I will never forget the day I saw the email in my inbox, we were so excited to open it and receive the results! They are in fact identical, and I feel reassured that AlphaBiolabs tests up to 42 DNA markers – double the industry standard for DNA testing.

“I highly recommend using them for twin DNA testing – the process was effortless and they’re a reputable and reliable company.”

Want to find out whether this test is right for you? Contact our friendly and knowledgeable Customer Services team on 01 402 9466 or email for more information.

Order a Twin DNA Test

Order your peace of mind Twin DNA Test online now, direct from our award-winning UK laboratory.