Are Identical Twins More Common After IVF

Dawn Davenport


IVF increases risk of identical twins

Ashley and Tyson Gardner’s reaction when ultrasound revealed

The Gardners had tried for eight long years to get pregnant. They had finally saved enough money to afford one IVF cycle. They were thrilled when they had 16 eggs retrieved, but their excitement was short lived when only two fertilized and grew into embryos””one high quality and one “iffy”. Both were transferred, and lo and behold both implanted and then split. They are now expecting quadruplets–two identical sets of twins!

Twin births in the US have increased a whopping 75% since 1980 primarily due to fertility treatment, but most of these births are of fraternal (non-identical) twins resulting from the transfer of two or more embryos. But did you know that women using IVF are also 2 to 8 times more likely to have identical twins?

Watch this video of Ashely and Tyson Gardner’s journey from the beginning to finding out they were expecting quadruplets.


Why Are Identical Twins More Common with Fertility Treatment

Doctors have many theories, but don’t really know why assisted reproduction makes it more likely for an embryo to split in two.  One theory is looking at the impact of ovarian stimulation possibly favoring the production of eggs more likely to create embryos with a tendency to split.

Another fascinating area of inquiry is focusing on the culture media in which the embryos are grown.  It is possible that this media makes the outer membrane covering the embryo (the zona pellucida) “harder” thus interfering with natural embryonic division. Others speculate that although we attempt to mimic nature when creating the culture media, we know that media differs from the environment of a woman’s reproductive tract. These difference include the absence of growth factors or cytokines and presence of higher levels of free radicals, and may result in changes to the embryo that make it more likely to twin.

It is also possible that the handling of the embryos during IVF damages slightly the outer membrane covering the embryo making it more prone to splitting.

Factors that May Increase the Chance of Monozygotic (Identical) Twins after IVF

  • Using donor egg
  • Mom being under 35 and using her own eggs
  • Embryo(s) grown to blastocyst stage (5 day) before transfer
  • Use of intracytoplasmic sperm injection
  • Assisted Hatching

While adorable, twins are at a significantly higher risk of prematurity and complications often lasting for life.  Twins from infertility treatment and identical twins are at an even higher risk. The good news is that research had found that 95% of identical twins after IVF have two amniotic sacs, avoiding one of the riskiest twin pregnancies where both babies are in the same amniotic sac.

The increased chance of having monozygotic twins adds further incentive for anyone with the above risk factors to seriously consider elective single embryo transfer (eSET), to lower the chance of higher order multiples, such as triplets or quadruplets.

Have you ever heard of someone having identical twins after infertility treatment?


Image credit: CNN “Ultrasound SHOCK! A mom-to-be’s priceless reaction!”

14/10/2014 | by Dawn Davenport | Categories: Blog, Infertility, Infertility Blog | 10 Comments

10 Responses to Are Identical Twins More Common After IVF

  1. Avatar Megan Klupshas says:

    I had identical twin girls after IVF. I was 35 y/o and it was the second cycle. I guess I am in the 5% with no membrane. I have mono/monos! Very scary and lots of bed rest, but they are healthy 3 year olds now!

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  3. Avatar Shana.E says:

    Iam a proud mother to 3 sets of twins and they were all conceived naturally. My twins are all fraternal- boy girl, boy girl and two boys. I’ve had my tubes tied for 11 years now and want to have more babies. I had a consult at the fetitily clinic and Iam only covered for one IVF cycle and they told me that one healthy baby is the goal. Ive been looking for identical birth rates through IVF because I wouldn’t mind having twins a 4th time. I just wanted to know my chances.

    • Dawn Davenport Dawn Davenport says:

      The vast majority of twins born via IVF are not identical. Most result from the transfer of two embryos during IVF.

  4. Avatar Ally says:

    I had two female friends end up with identical twins after IVF. Unfortunately both of them ended up delivering their twins more than 2 months premature and had a very difficult time. A third friend of mine almost had identical twins after IVF, but one of the twins miscarried at about 12 weeks so it ended up a single pregnancy.

  5. Avatar AnonT says:

    Thanks for making this post Dawn. I just think there is a major disconnect between what would be “best practice” and what is actually done. I think one of the biggest thing for this is lack and health insurance thus the insane cost of IVF. And the second is emotional states of the couple that reaches the point of IVF – that is we go in wanted maximize our chances of getting pregnant. Even given the greater likelihood of splitting, I know that I was recommended to transfer 2 embryos due to my age. I’m guessing that the 2-8 times greater likelihood of having an embryo split is still lower than the likelihood of a successful cycle in our age bracket. So it is very difficult, these decisions. Ideally we would all be transferring one at a time but I don’t think this is the reality, especially for older women. I’m very happy that the IVF cycle worked for the Gardners…but if it were us, I think I would be more terrified than happy about carrying quads.

    • AnonT, I agree with all your points. Plus, I’d add that when we assess risks, most of us think the bad won’t happen to us. Our twin pregnancies will make it to 36 weeks at least, our babies won’t be sick, our embryos won’t split more than we want, etc. I imagine the Gardners are a mix of excited and terrified!

  6. Avatar Jen says:

    I have 18 month old identical twin boys after 8 years of trying. I thought it might have something to do with having ICSI done.

  7. Avatar Leah says:

    Oh dear, it appears I’m a statistic! We had fraternal twins through IVF and, less than four years later, had identical twin boys naturally.

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