Are Identical Twins More Common After IVF
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!” Sources:
- The risk of monozygotic twins after assisted reproductive technology: a systematic review and meta-analysis. Hum. Reprod. Update (2009) 15(1): 45-5.doi: 10.1093/humupd/dmn045
- Monozygotic twinning: an eight-year experience at a large IVF center. Fertility and Sterility, Volume 94, Issue 2, Pages 502-510, July 2010