Clearing up confusion over transferring only one IVF embryo at a time (eSET) or transferring multiples to increase the odds of success.
Couples using in vitro fertilization (IVF) procedures are usually warned about the risks of multiple gestation (twins or more). All other things being equal, it is always better to conceive one child, called a singleton pregnancy. However, traditionally IVF physicians have been transferring more than one embryo at a time, sometimes two or three or even more.
The reasons for this apparent inconsistency have often been confusing for patients. In this blog, we would like to outline the pros and cons of elective single embryo transfer (eSET). Is eSET the best choice for everyone?
The objective or a goal of any fertility treatment should be obvious – a healthy baby. Historically, the transfer of multiple embryos with IVF was performed to maximize pregnancy rates, but frequently the practice resulted in twins, triplets and other multiple gestations.
IVF with multiple embryos often can lead to complications caused by premature birth. It is well known that conceiving one baby will create the healthiest possible scenario for a healthy newborn and a healthy mother. The question is how do we get there?
Easy answer for a healthy mother and child is single embryo transfer
The answer should be easy – just transfer a single embryo at a time and chances of a multiple or twin pregnancy will be very, very low. While it is possible for any embryo to split and create an identical twin pair, this scenario is rather unlikely and usually happens in a tiny minority of patients. However, in many cases this conservative approach may decrease chance of success and result in a low pregnancy chance per cycle of treatment.
It is not always possible to have the optimal chances of success. But getting as close as possible is why IVF physicians have historically opted to transfer multiple embryos. They – and their patients who willingly choose multiple embryo transfers – know the risks of a multiple pregnancy and the increased chance that it could occur. About 30 percent of all IVF pregnancies result in twins, with another 3-4 percent being triplets or more. The general birth rate for twins in the United States is 3.5 percent.
Better answer is using PGS to identify the best single embryo for transfer
But there’s a better option now, and IVF physicians and patients are increasingly choosing it: Preimplantation genetic screening, or PGS. The major cause of failed embryo implantation – in IVF or naturally – is a genetic flaw in the embryo that prevents it from implanting or causes a miscarriage after implantation.
PGS tests IVF embryos for aneuploidy, which is an abnormal number (too few or too many) in all 23 chromosome pairs. The most common instance of aneuploidy is Down syndrome (trisomy 21), which is an extra chromosome in pair # 21.
With PGS, we evaluate IVF embryos and can select one without such genetic defects for implantation. This healthy embryo – and we wouldn’t know it was healthy without PGS – increases the chance of pregnancy success when the patient elects to implant this one embryo, rather than two or more. Aside from pregnancy success, PGS also greatly reduces the chance of the mother having a baby with a birth defect.
Is PGS a good idea for IVF patients? Yes, in the vast majority of cases, particularly when the parents want to use eSET to reduce the chance of twins or more. In 2016, the The American Society for Reproductive Medicine (ASRM) sent out a brief communication on Preimplantation Genetic Screening for Aneuploidy Technology. This document suggested that the use of PGS as a screening test for IVF may end up with higher live birth rates with increased eSET frequency. This is the first international society suggesting that PGS might yield better outcomes and should be considered to reduce multiple pregnancies.
If the embryos are not screened genetically, we’re back to the reality of a decreased success rate with eSET. But even that isn’t so clear cut.
Most research shows that for unscreened embryos, chances of conceptions with two eSETs in a row are very similar to a double embryo transfer done at one time. But in statistical terms, this decreases the “per cycle” success rate.
Individual circumstances of the couple’s testing and embryo development should direct decision making in these circumstances. Patients are encouraged to discuss their own specific consideration with a physician to make a decision that is most appropriate for them.
IVF is not a cookie-cutter option, and an individualized approach is advocated. We at Advanced Reproductive Medicine strive to provide personalized care and work with our patient to ensure the best possible scenario and the highest chance of success, safely.
The “but” to the above
Caveat: The scenarios described above are most applicable to couples who are using an embryo created with their own eggs and sperm. Scenarios involving a donor egg, donor sperm or donor embryos create different circumstances and deserve a separate discussion.
Insurance coverage is also a big factor, based on the recent research we helped conduct. Researchers evaluated factors associated with using eSET and pregnancy outcomes from 2004 through 2012. The study encompassed analyses of cycle outcomes in women less than 38 years old.
While the use of elective single-embryo transfer has increased dramatically, researchers found it is more likely in states with infertility treatment insurance coverage. About 48 percent of all procedures occurred in the six states with the greatest use of assisted reproductive treatments. Colorado is not one of the these six, so patients desiring eSET should check with their individual policies about coverage.
There are issues or situations when eSET may not be the best procedure for a woman. These generally include:
- She has not been able to produce healthy embryos
- She has had previous unsuccessful IVF.
But all women have the option of considering eSET and should discuss it with their IVF physician.