One of the most important decisions you have to make with your fertility specialist during IVF treatment is how many embryos to transfer. In an IVF cycle, your eggs are combined with sperm in the lab. If all goes well, some of the eggs will be fertilized and will develop into embryos.
When they are ready, usually three to five days after fertilization, a certain number of embryos will be transferred to your uterus. One or more of these embryos may implant and grow into a baby.
The old “rule of thumb” was to transfer two or three embryos, depending on the woman’s age and history with IVF, but never less than two. In recent years research has begun to support eSET, or elective single embryo transfer, as a successful treatment for some women, which also reduces the risk of multiple births.
Success of eSET
Research studies have assessed the success rates of pregnancy and live birth based on the number of embryos transferred during an assisted reproductive technology (ART) procedure, according to the Centers for Disease Control and Prevention (CDC). These studies found that women who had a good chance of success with IVF, who chose to have a single embryo transferred, had similar success rates to women who had more than one embryo transferred. And almost all of the babies delivered were singletons.
The American Society for Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) have issued guidelines for elective single embryo transfer.
In general, women who are 35 or younger and have good quality eggs and embryos are good candidates for eSET. In programs who do blastocyst transfers (on day 5 after retrieval) when there are additional good embryos to freeze or for women who opt for preimplantation genetic screening (PGS) with subsequent frozen embryo transfer (FET), the use of eSET may be expanded to more women and even to many women over age 35. However, every woman’s circumstances and treatment is individual, and this is a decision you need to make with your reproductive endocrinologist and your partner.
Risks of Multiple Births
Perhaps you’ve noticed the greatly increased number of twins in the last several years. Many of these are due to IVF. Some people like the idea of having twins, and “getting their family done at once.” But most people are not aware of the risks of multiple births to both the babies and the mother.
Multiple births (two or more) increase the risk of premature birth and low birth weight, according to the CDC. About 60 percent of twins are born prematurely. These babies may require special care and may even have life-long problems such as developmental disabilities. Women carrying more than one baby have greatly increased risk of needing a Caesarian section, which calls for longer recovery and may have complications.
Another area people tend to ignore is the expense and difficulty of caring for two babies at the same time! Do you have a support system to help you if you wind up with more than one baby? What are the practical and personal limits of what you can do? It’s important to think about as you decide if single embryo transfer is right for you.