MARCH 27, 2018
Twins DNA Testing: Identical or Fraternal?

Are Your Twins Identical or Fraternal?
Without a doubt, this is a question all parents of look-alike twins get every time they break out the double-stroller, pack up the extra-large diaper bag, and go out into the world. If your parenting life is double-the-fun, you may think you already know the answer to that question.ย But do you really?ย In a nutshell, unless an ultrasound showed that your babies shared a single amniotic sac, only twins DNA testing can tell you for sure whether theyโre identical or fraternal.
Basic Types of Twins: A (Very) Quick Primer
Before the widespread use ofย DNA testing, medical professionals (and therefore parents) assumed that, if twins had their own amniotic sacs and their own placentas, then they must be fraternal. Not so fast!
Fraternal twinsย come from two eggs being fertilized by two sperm. The zygotes implant separately, have their own in-utero โcondos,โ and can be girl/girl, boy/boy, or boy/girl.
Identical twinsย come from a single fertilized egg that splits in two. This division happens usuallyย around days 4 or 5, and after the placenta and amniotic sac have started developing.
BUT :
If the fertilized egg splits before the placenta and amniotic sac normally start forming for identical twins, say around days 2 or 3, then each zygote develops its own sac and placenta.
So what could look like fraternal twins to medical pros is actually a set of identical twins!
Twins DNA Testing: Argon & Aldridge
We recently didย twins DNA testingย (Twin Zygosity Test) for two very handsome young men from Idaho named Argon and Aldridge, who were born in January, 2018. They areย Dichorionic Diamniotic (Di/Di) twins, which means each of them had their own amniotic and chorionic sacs. Although the majority of twins of this type (70 %+) are fraternal, the boysโ parents wanted to confirm their relationshipโand the only sure way to do that is with twins DNA testing.
Their mother, Ally, who writes a lovelyย parenting blog, told DDC: โIt doesnโt really matter to us if theyโre identical or not. Yes, weโre curious, but I think the boys would eventually want to know if theyโre identical or not.โ

How It Works
- DDC sends DNA-collection materials, swabs, and directions to test participants (or to their parents, if they are minors)
- Buccal (cheek) swabs are used to collect the DNA from each participant. Itโs non-invasive, fast, andย pain-free
- The customer mail samples back to the lab where they are tested and analyzed by our team of PhDs. And in just a few days, the report is posted to a secure online account for viewing
A probability of relationship is given for twins DNA testing, just as it is forย paternity-test results, except in this case the probability is for whether the twins are identical or fraternal.
Facts about Twins
Here are some quick, fun,ย facts about twins:
- 1 in 90 live births are twins
- If you are a fraternal twin, you have a 1 in 17 chance of having twins yourself; but if youโre an identical twin, your chances of having twins are the same as for non-twins
- One-third of all twins born in the U.S. are identical
- The average birthweight for a twin is 5 lbs 5 oz
- Children of identical twins are genetically half siblings
- If identical twins were to marry other identical twins, their children would technically be cousins, but their DNA relationship would be that of full siblings
Final Thoughts about Twins DNA Testing
With todayโs advances in DNA science, there is absolutely no good reason to wonder whether or not twins are identical or fraternal. As they get older and their brotherly bond deepens, Argon and Aldridge will be thankful that their parents had this test done on their behalf.
Thanks to Argon and Aldridgeโs parents and siblings for agreeing to share their story. Follow them on Instagram: @theblackandwhiteblogco
About DNA Diagnostics Centerย (DDC)
DNA Diagnostic Center is the world leader in paternity and relationship testing. We serve healthcare professionals, government agencies, and individuals around the world to determine family relationships with trusted accuracy.
More Questions? Donโt hesitate to call us: weโre here to help!
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