Why do we recommend elective single embryo transfer?

By: Michelle Catenacci, MD

Patient desires

Many couples that come to us have had a long and difficult journey with their infertility.  When discussing treatment options, we discuss the risk of twins or high order multiples (triplets or more) that exist with the different available fertility treatment options.

However, to many that are trying to conceive, multiples are thought of as a blessing and not a risk.  “The more the better”, and, “Two for the price of one”, are common replies that we get from couples when discussing twins.  It can be difficult to convey that there is more risk involved with twins compared to a singleton pregnancy and that it is safest for both mom and baby to have one baby at a time.

Recent changes in recommendations

Recently, the Society of Assisted Reproductive Technology (SART) and the American Society for Reproductive Medicine (ASRM) issued new guidelines and recommendations for the number of embryos to transfer in order to encourage physicians to increase use of elective single embryo transfer (eSET).

With an elective single embryo transfer, a single embryo is selected from a larger group of embryos to be transferred.  Excess embryos can be cryopreserved for future attempts at pregnancy.  In general, it is recommended that patients with a high chance for success should strongly consider having eSET.  Those patients include younger women (37 and under), women with normal embryos after preimplantation genetic testing for aneuploidy (PGT-A), and women using donor eggs.

Transferring one embryo at a time will not decrease the “cumulative” pregnancy rates for that IVF cycle – when looking at overall pregnancy chances with both the fresh transfer cycle and also any subsequent frozen transfer cycles.  Single embryo transfer will, however, significantly decrease the overall risk of twins.  For example, at our clinic, we see approximately 65% live birth with eSET for embryos that have been screened for aneuploidy using PGS (also called PGT-A).  The risk of identical twins is under 1% in this situation.  If we transfer two embryos, the pregnancy rate is about 90%, but the rate of twins is 65% with a 1% risk of triplets.  At AFCC we try to encourage patients to transfer just one PGT-A embryo in hopes of helping them have a healthier single pregnancy.

Risks involved

There are increased rates of complications with twin pregnancies.  Some of these risks are for the mother herself.  Maternal complications that are increased in twin or higher order multiples include preeclampsia, gestational diabetes, worsening anemia and severe nausea and vomiting in early pregnancy.  There is also an increased risk of abnormal placental attachment which can cause bleeding and other complications during pregnancy or at delivery.

Women pregnant with multiples are more likely to have a cesarean section for delivery.  For the babies, there are significantly increased rates of preterm labor and delivery, small for gestational age babies and growth restriction.  At times delivery will occur near or just before the gestational age of possible viability leading to death or long-term complications for one or both twins.  The risk of cerebral palsy in twins is more than four times higher compared to a singletons.  Twin babies are also more likely to be stillborn or die in the first month after birth as compared to single babies.

Conclusion

Our goal is to provide safe and high-quality care to our patients.  When we recommend eSET we are striving to give the best possible outcome for the patient and their unborn child.  When planning to move forward with IVF or egg donation it is important to know the current practices the fertility program you are working with, and their overall success and experience with eSET.  For patients that have a high chance of success, transfer of a single embryo should be seriously considered even though the initial pregnancy rate from transferring two embryos is higher than if we transfer one.

See our IVF Success Rates

See our egg donation success rates

Michelle Catenacci, MD

Dr. Michelle Catenacci is a reproductive endocrinologist and infertility specialist.
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