I dedicate this post to future twin mothers everywhere.  The majority of the population has no idea what the actual differences are between identical vs. fraternal twins.  As a twin mom, myself, I am begging anyone who reads this to share it with others so we can educate those around us.  Knowledge is power.

Introduction

I am a proud mother of fraternal boy/girl twins and like every mother of twins, I am constantly asked whether my twins are identical or fraternal.  I am not sure why but there is a ton of confusion that exists on this topic. Even some highly educated people do not actually know the difference between the two.  I am the last person in the world who should be teaching a biology class but this is one subject that I know about from personal experience so grab a pen and pad or open up your notes app in your iPhone and be prepared to be schooled.  The following information reflects the two most common types of twins. There are some very rare twin types as well as different genetic mutations that may result in exceptions to these rules.

Part One

Identical twins are ALWAYS the same gender.  This is true without exception.  Identical twins are virtually an exact genetic match for one another.  Their cells are primarily the same in every single way.  That is why people who are not around them on a daily basis have trouble telling them apart from one another.  Boy/girl twins are always fraternal twins.  This is not up for debate.  It is fact. 

Part Two

If a parent tells you that their twins are actually fraternal and not identical, you should believe them.  I know this sounds blatantly obvious but many people have asked me if my twins are identical and I would tell them no and they would often follow up with the question:  “Are you sure because they look a lot alike?”  I believe some of their confusion stems from the fact that because fraternal twins are siblings, they often do look a lot alike. Plus, fraternal twins often look even more alike than other siblings do because they are exactly the same age.  I think if any non-twin siblings were exactly the same age that they would look more alike as well.

Part Three

When does a woman know if she is carrying identical vs fraternal twins?   The answer to this question varies on a case by case basis.  Identical twins, come from just one embryo that is inexplicably replicated.  This is why identical twins look almost exactly alike because they actually came from the exact same sperm and the exact same egg.   It is sometimes harder to determine if twins are identical on an ultrasound but typically the answer can be determined by the end of the first trimester. However, in rare instances, it cannot be determined until after the twins are actually born.

Fraternal twins, on the other hand are easier to spot.  Fraternal twins come from two different eggs and two different sperm and are genetically just like any normal siblings. The only difference is that they experience gestation together and are born together. Typically during ovulation, women drop one egg each month but when a woman gets pregnant with multiples, she drops more than one egg at a time.  As a result, more than one egg has the opportunity to get fertilized resulting in her getting pregnant with multiples.

Conclusion

To recap:

  1. Identical twins are the same gender.
  2. Twin parents know whether they have identical or fraternal twins so when they tell you, believe them.
  3. Identical twins are a result of an embryo split into two
  4. Fraternal twins are a result of more than one egg being fertilized at the same time
  5. Fraternal twins are genetically no more alike than regular brothers and sisters.

Extra Credit

Please… PLEASE never under any circumstances ask a mom of twins the following question:  “Are your twins natural or artificial?”  First of all, whether parents needed the help of a doctor to conceive their twins or not, is really none of your business.  If a twin mom volunteers this information to you, that’s one thing but if she doesn’t just be happy for her and don’t give it another thought.  Secondly, I assure you that if a woman did require medical help in order to conceive her twins, those children are a real as any other children.  They are by no means artificial.

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Author

Marianne Badurina is a happily married Mommy of 2 1/2 year old twins working in Marketing who loves everything creative from singing to writing to cooking and crafts. She started "The Marvelous Misadventures of a Working Mama" blog (or The Marv Mis for short) to connect with other Moms who love to share tips and laugh through the struggles of all that is Mommy!

3 Comments

  1. Some twins which are ‘suppose’ to be fraternal are actually identical though. Something like 30% of fraternal twins are wrongly classified. (mum to twin boys)

    • themarvmis@gmail.com

      Hey Laura,

      Thanks for your comment. Did this happen to your boys? If so did they have to take a DNA test to see?