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Single Embryo Transfers

ohn S. Rinehart, M.D., Ph.D., JD

At Reproductive Medicine Institute, we strive to offer our referring community and our shared patients the most current information on Assisted Reproductive Technologies (ART). In this blog we discuss elective Single Embryo Transfer, known as eSET.


Single Embryo Transfer

John S. Rinehart, MD, PhD


IVF (in vitro fertilization) revolutionized the treatment of infertility. There are over 8 million children born world-wide as a result of this technology. However, like all new technology, IVF has had a dark side- the generation of high-order multiple gestations (twins, triplets, quads, and more). Recent advances in technology have opened the possibility of removing this risk. So how did this all start, what has changed, and how can the new technology help couples have healthy children.


What is wrong with twins? (or more)


Practically everything! Every complication that puts a child at risk is elevated for twins and beyond. The primary problem is prematurity, where the children are born very prematurely, will result in their being in the neonatal intensive care unit for weeks and can lead to a lifetime of complications. Over 60% of twins and almost all triplets or higher are born prematurely (< 37 weeks and a normal pregnancy goes to 40 weeks). Other complications include low birth weight, fetal demise, and twin-to-twin transfusion syndrome (where one twin gets all the blood supply and the other twin does not). The mother’s risks are increased with multiple gestations. These include preeclampsia (high blood pressure) placental abruption (where the placenta separates before the child is born), gestational diabetes, postpartum hemorrhage, and C-section. The point: women were designed to have one child at a time, anything more than that increases the risks for bad outcomes for both mother and child.


How did this problem start?


IVF is notorious for twins, triplets or more. The problem began at the start of IVF. Initially, the pregnancy rates for IVF were quite low. Furthermore, for any given embryo the chance of that embryo resulting is a child was extremely low- as low as < 5 %. In addition, the freezing of embryos had not yet been developed. So, faced with no prospect of freezing embryos for future use and very low chances of success, patients and physicians elected to transfer more than one embryo during a single cycle in order to increase the chance for pregnancy. Remember, in the early days of IVF, there was no insurance coverage. Even today’s IVF insurance coverage is mandated in only 16 states- IVF was expensive and anything that increased the chance for a successful pregnancy would help to reduce the cost. In fact, it was not uncommon to transfer 4 or maybe even more embryos during a single cycle.


What changed?


Technology advancements allowed embryologists to create embryos that had a much better chance of resulting in the birth of a child. Culture media improved and thus embryos could be grown for 5-6 days in the lab. This permitted nature to select better embryos. The most recent addition was the ability to test embryos to determine if they have the correct number of chromosomes (or a euploid embryo). The most common reason that an embryo fails is due to aneuploidy (or the wrong number of chromosomes). Testing the embryo to determine that it has the correct number of chromosomes significantly increases the chance that an embryo will result in the birth of a healthy child. As the quality of the embryos increased, so too, did the multiple gestation rate.


What can be done?


Knowing that the main reason for failed implantation and knowing that the risk of abnormal embryos increases with age, permits the development of guidelines for judging how many embryos to transfer. The American Society for Reproductive Medicine (ASRM) has published guidelines to help couples and physicians determine how many embryos to transfer. The table is based upon the age of the female, whether the embryo is euploid, and whether the embryo has been cultured for 3 days (cleavage) or 5-6 days (Blastocyst).


Financial considerations often play a role in deciding how many embryos to transfer. Many patients in Illinois have coverage for IVF. For couples without coverage, each transfer costs a considerable amount of money. There is no easy way to decide what to do in these circumstances. The point is that the number of embryos to transfer is a balance between the health of the child/mother and the chance for a pregnancy. Discussions with the embryology team and the physician can help.


At RMI, our goal is for the patient to have a healthy, successful pregnancy. We understand that each patient experiences their own unique journey through fertility. Our team is here to provide your patients with the information needed to meet their needs while giving them the best chances of having a successful pregnancy and a healthy baby.