Single embryo transfer
Why transferring one embryo at a time lowers the chance of twins, and how we decide together how many embryos to transfer.
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The number of embryos transferred should be kept low enough to avoid multiple pregnancies, while still giving you a good chance of pregnancy.
Why the number of embryos matters
In an IVF cycle, the number of embryos placed in the uterus is decided by you and your doctor. In general, transferring two embryos leads to a twin pregnancy rate of about 25 to 30%, compared with less than 1% when one embryo is transferred. Twin pregnancies carry more risk for both parent and babies, so single embryo transfer (SET) greatly reduces multiple pregnancies.
How single embryo transfer works
The chance of pregnancy from a single fresh transfer is somewhat lower than from transferring two embryos at once. If pregnancy doesn’t happen after a single embryo transfer, a frozen embryo is thawed and transferred in a later cycle.
Taken together, this “one plus one” approach gives a chance of pregnancy similar to transferring two embryos in the fresh cycle, while nearly eliminating triplets and higher-order multiples and greatly reducing twins.
How we decide together
We individualize the number of embryos based on your age, the embryos’ appearance (morphology) and the stage at transfer (day 3 or day 5). For younger patients with good-quality embryos, one or two embryos may be transferred.
Our team sits down with you and talks through, in detail:
- Your chance of pregnancy with each number of embryos transferred
- The likelihood of a multiple pregnancy
- Your goals for your family and how you feel about fetal reduction
For women 35 or younger with several embryos developing on day 3, we extend culture to the blastocyst stage, which makes it easier to choose the embryos most likely to implant. We also offer the option of transferring one embryo and freezing the other instead of transferring two. If pregnancy doesn’t happen, the frozen embryo is thawed and transferred. This approach gives a chance of pregnancy comparable to transferring two embryos, with far fewer twins.
Genetic testing and embryo selection
Chromosome testing of embryos helps us select the embryo most likely to lead to a pregnancy and delivery, which makes choosing a single embryo for transfer easier. Learn more in genetic screening and PGT and frozen embryo transfer.
This article is general information, not medical advice. Every situation is different, so talk with your doctor about yours.
