Can Identical Twins Be Opposite Genders?

Can Identical Twins Be Opposite Genders or not

Author: Stephanie Ernst

Identical twin parents will all nod their heads here when you ask them what one of the silliest questions they’ve ever been asked is.

“Is it a boy and a girl?” (I seriously heard all of  you out there rolling your eyes right now!)

Can Identical Twins Be Opposite Genders?

Here’s the tea, though: It can happen, but it’s super rare.  We’re talking you’ve got more chance of winning the lottery rare! But it does happen, and it can occur in a few ways.

boy girl identical twins

Turner Syndrome

The most widely recognized way it can happen is when the egg doesn’t split properly or a genetic problem. The girl of the twins can have Turner Syndrome, where she is missing an X chromosome. 

Turner Syndrome has a range of how it affects women, but there is a chance of heart problems, and the girls are usually infertile.  However, it is not life-limiting in most cases, and many Turner patients go on to live happy healthy lives.  The diagnosis is confirmed through genetic testing.

can identical twins be boy girl

Semi Identical Twins

We’re only just beginning to learn about this special type of twinning in a new area of research.  It’s not really known why it happens– but the twins are genetically fraternal, and still share a placenta.  There are some theories about 2 sperm and one egg, or 2 eggs fusing, but the reality is that we simply don’t know what this happens.  This article goes into the science, if you want the nitty gritty of it all.

Identical Twins Opposite Genders

Important Things To Know

What’s really essential for all parents of twins is that regardless of the gender of your twins, your care team should be doing standard tests based on the number of placentas they see.  Even if the twins are different genders, but they see only one placenta – that means you should be getting screening as identical twins.

Shared placentas have different risks, and it’s essential to establish the number of placentas early on. 

TTTS and TAPS are just some of the risks for twins sharing a placenta. 

When the babies are born, you may also undergo genetic testing and checkups if it’s determined that your babies have shared a placenta.  It’s really important to know that you may not get answers straight away, but a good team will keep you informed of next steps and processes, and help you with the support you need.

stephanie Ernst TAPS twins

Stephanie Ernst is a freelance writer and self-proclaimed TAPS Nerd. She’s the TAPS Support Foundation‘s founder and spends her free time raising awareness of the issues facing parents of twins.  Her own experience with Twin Anemia Polycythemia Sequence (TAPS) and feeling the isolation of this diagnosis drives her determination to change screening protocols worldwide, support twin research, and raise the profile of multiples’ rights.


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