Fertility Blog

Promoting eSET - Average number of embryos transferred at PFC compared to SART/other clinics

If you are a patient you probably think that the biggest problem with IVF treatment is that not every cycle results in a pregnancy or baby. But if you are a Physician, you will know that the biggest problem is the high incidence of multiple births that result from fertility treatments. And you will know that it is a global problem. The United States and Canada lead the world in the multiple births table, where over 30% of all IVF births result from twin or higher order deliveries. We are the countries that transfer a single embryo least often, in fewer than 20% of all cycles. In contrast, countries like Sweden and Australia, where single embryo transfer is mandated by law for most patients, multiple births make up about 5% of deliveries and 70% of patients transfer one embryo in an IVF cycle.

Even with the best medical care, the consequences for mother and children are significant when more than one baby is present in the uterus. Such pregnancies almost always end prematurely, with infants that are underweight when born. Complications for the mother are increased significantly too, as is the risk of needing a caesarian section.

1. This reduction was due in large part to the advent of blastocyst stage (day 5 post retrieval) transfers which facilitate better embryo selection of viable embryos. But this technology has failed since the number of patients transferring 2 embryos has increased from around 10% to 50% during the same time period. Even when good quality blastocysts are available for transfer, patients are still transferring 2, and the result is that consistently over the last 15 years, almost half of all IVF deliveries have been twins.

The problem of IVF multiple pregnancies is being discussed and solutions have been proposed that include obtaining insurance coverage for IVF treatment, changing the way the government reports IVF success rates and better educating patients2. However, we have the tools now to address the problem without waiting for others to come up with solutions. For example, as mentioned above, our ability to grow embryos to the blastocyst stage is a big advantage over the previous practice of transferring embryos on day 3 after retrieval. We are much more confident now about the quality and developmental potential of the embryos being transferred, such that we can transfer just a single embryo in most IVF cycles. To further enhance embryo selection, we are also employing genetic screening of blastocysts, and other advanced techniques like time-lapse imaging, to ensure that the embryo being transferred is genetically and developmentally normal. PFC has been a national leader in the use of these technologies to allow single embryo transfer for a number of years now, and we are have not compromised success rates in the process. In addition, we have developed and implemented a very successful embryo freezing program, using a rapid freezing technique called vitrification to preserve blastocysts remaining after transfer. We have been vitrifying embryos successfully since 2007 and the program has been so successful that patients can transfer just one fresh embryo safe in the knowledge that their frozen embryos will be available if and when they are needed. And even with frozen embryos, we are transferring just one at a time. In 2013 we performed over 550 frozen embryo transfers and 83% of these used just a single embryo.

We are very proud of our efforts to get most patients to transfer one embryo at a time, and we have even been successful in patients over age 35, and additionally in patients older than 40. The patients at the older end of the spectrum have the greatest risk of having genetically abnormal embryos, and historically multiple embryos were transferred with the assumption that most of those that were abnormal would fail to implant. But that approach led to miscarriages and loss of valuable reproductive time for many women, so we now do the genetic screening before transfer to avoid these problems. Not all patients will have normal embryos to transfer, but those that don’t will be able to have a repeat IVF cycle in a much shorter time. And transferring a single genetically normal embryo reduces the miscarriage rate significantly and allows older patients to start out with a healthy singleton pregnancy. The outcome data for patients with genetically tested embryos is shown in the table below.

Table 1. Pregnancy outcome and average number of embryos transferred by age group in 2013. Patients had their embryos vitrified while awaiting genetic testing results, and returned for transfer of genetically normal embryos.

The data for all IVF clinics across the US3 show that the number of embryos being transferred remains at about 2 for younger patients (oocyte donor recipients and patients <35), suggesting that twin pregnancies is going to continue to be an issue going forward. In the older patient groups, the number is approaching 3, which will also give rise to significant numbers of twin and even triplet pregnancies. At PFC we have taken a very proactive approach to this problem and have been successful in performing elective single embryo transfer across all age groups, transferring significantly fewer embryos and reducing the risk of multiple pregnancy. Our moto here at PFC continues to be “one healthy baby at a time”.

Table 2. Average number of embryos transferred in fresh IVF cycles in the US in 2012. Data from the Society for Assisted Reproductive Technology (SART)3.

  1. Kulkarni, A.D., et al., 2013, Fertility Treatments and Multiple Births in the United States, New England Journal of Medicine, 369;23.
  2. Johnston, J., et al., 2014, Preterm births, multiples, and fertility treatment: recommendations for changes to policy and clinical practices, Fertility and Sterility, article in press.
  3. https://www.sartcorsonline.com

- Joe Conaghan, PhD
PFC Lab Director

Ready? Let's Connect.

We're here to go at your pace and answer any questions you have. Get in touch when you're ready. We'll be right here.

Request a Consult Contact PFC

Translate page