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Identical or Fraternal? Doing a Twins DNA Test

Identical or Fraternal? Doing a Twins DNA Test

twins DNA test twin babies sleeping

Last updated on February 12th, 2024 at 04:07 pm

“Are they identical?” Every twin parent knows that this is probably question #2 in the official question list from strangers about your twins, even if you have opposite-sex twins. Question #1 being, “Are they twins?”, of course.

In my case, I had two girls whom my doctor had informed me were fraternal at the very first 8-week appointment. So my answer was always, “No. They look alike, but they are fraternal.” twins DNA test

And then the rest of the typical twin questions would continue. Sometimes, I would hear, “Are you sure they’re not identical?”

That would lead to an explanation of the biology of twinning and I would explain that we saw a solid separation between two amniotic sacs which clearly formed early on, so it was consistent with the fertilization of two separate eggs (dizygotic) that results in fraternal twins, as opposed to a single egg that splits (monozygotic), creating identical twins. twins DNA test

twins DNA test baby twins

As I learned more about twin zygosity and identifying twin types, I began to question my doctor’s assessment.

Dr. Sean Daneshmand, a perinatologist at the San Diego Perinatal Center explains that, “About one-third of all identical twins have separate placentas,” and that medical practitioners are more concerned with the number of placentas instead of the zygosity. twins DNA test

While parents want to know if they are expecting fraternal or identical twins, the doctors are focused on what it means for patient care. “As far as the management of the pregnancy, whether (it’s) fraternal or identical, it really boils down to the number of placentas. That’s where complications begin.”  So this might explain why my doctor was so focused on placentas.

Finally, when my “big sister” from my local twins club first met my girls and was adamant about them being identical, I had serious doubt. I admitted that they looked very much alike, had the same blood type, and were nearly identical in height and weight at birth. twins DNA test

Could they be identical? Could my doctor have made a mistake? And even if she was wrong in her assessment of dizygotic/fraternal twins, would it make any difference?

As a parent, are there reasons beyond curiosity that I should be aware of? Do my girls need to know?

I Had to Weigh the Pros and Cons of Finding Out


We can answer those stranger questions with confidence. twins DNA test

My girls can have a strong sense of identity in knowing how they are related.

Personally, it might help solve a future dilemma of deciding to have more kids if we were “at risk” for having more twins—i.e. if they were truly fraternal, it could mean that I’m prone to multiple ovulations and might have more twins (yikes!) vs. if they were identical, the probability is very low for having more.

twins DNA test toddler twin girls


It could be expensive. My pediatrician told me that a twins DNA test would cost about $300+ and it’s not covered by insurance. 

Would I have to subject my kids to a painful, unnecessary procedure?

Would I be doing this just to satisfy the curiosity of strangers?

Could there be some level of disappointment in learning the answer?

The Answer

But my own curiosity was killing me! So I asked around in my twins club and looked up several DNA testing companies and I was pleasantly surprised to find that the price range was $79-150 and it involves a painless swabbing of the cheeks. twins DNA test

Results are emailed within two weeks of the lab receiving the samples, and for an additional fee you receive official printed documents detailing the results.

So we took the dive into the twins DNA test and I ordered the swabbing kit online. I received the kit in about a week and swabbed each of my girls’ cheeks with the two large cotton swabs for each girl. I carefully repackaged everything in the kit and mailed it back to the lab with great anticipation.

Two weeks later, I got an email response with a lab report attached. It read at the top, “….the lab results indicate a 99.997% match with the 1st sample.” It was a complete shock! I quickly realized that my twin club big sister was right. She saw something that I didn’t see. It was so obvious to others, but I didn’t see it myself. How could I be so oblivious?! twins DNA test

Clearly, I was the last to know. It sounds so ridiculous to say, but I really wanted to believe the idea that we had from the beginning; the one that my doctor had so authoritatively declared. It’s not so much about whether my twins are fraternal or identical, but holding onto a perspective that was clearly wrong.

twins DNA test

I’m actually very glad that we did the DNA testing because it literally set the record straight. And it was one of many turning points in the path of parenthood that showed me that sometimes the gut instinct is often more correct than what many experts have declared. twins DNA test

I had observed that my girls appeared the same in so many different ways, but I had defended the expert opinion.  Since then, I have become skeptical about generalized opinions and tend to seek out more evidence in making any important parenting decision. The twins DNA test was one of those tools and it now gives me the confidence to say “yes!” with a smile when people ask if my twins are identical.

All content on this Web site, including medical opinion and any other health-related information, is for informational purposes only and should not be considered to be a specific diagnosis or treatment plan for any individual situation. Use of this site and the information contained herein does not create a doctor-patient relationship. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.

Christine Stewart-Fitzgerald

Christine Stewart-Fitzgerald After giving birth to identical twin girls and later a spunky singleton girl, Christine dove headfirst into the world of twindom- joining the board of the local twins club and became host/producer of the podcast Twin Talks, produced by New Mommy Media. She currently resides in Southern California with her girls and husband who hopes to someday get a male dog with “cajones”.

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