Success Rates

SART Statistics

In reading program brochures or browsing the internet, patients with infertility are often exposed to a bewildering assortment of graphs, tables and numbers, especially regarding “success rates” and individual assisted reproductive technology (ART) statistics. The term ART is meant to encompass all the various techniques of in vitro fertilization (IVF) including those using embryos derived from a woman’s fresh eggs or a donor’s eggs and either fresh or frozen embryos. (The list of included techniques continues to grow as the repertoire of IVF continues to expand.) The educated patient must be able to decipher meaningful data from these numbers; since a clear understanding of what factors may influence any individual patient’s outcome for success is essential. Many factors may affect not only the choice of a patient’s fertility program but also their specific chances of achieving the ultimate goal — a baby.

It is important to keep in mind that each ART program uses its own guidelines for patient selection, including the initial acceptance in, or rejection from, the program. Examples include clinics that use ART to treat women who would likely become pregnant with simpler, less expensive treatment or clinics that will not treat older women or other women with a poor prognosis to succeed. These entry or exclusion criteria significantly affect the outcome of treatment. Program statistics are mainly useful in the context of a discussion with a reproductive endocrinologist, as any specific patient’s chances of conception may be decreased or increased by individual factors, especially the medical history. It is also important to remember that what typically draws attention are the individual program statistics from in vitro fertilization. These statistics say nothing about the probability of conceiving as a result of the many other medical and surgical techniques that are used to treat infertility.

Both the American Society for Reproductive Medicine (ASRM) and the Centers for Disease Control (CDC), which compile the results of nearly every ART program in the United States, caution prospective patients not to compare statistics across programs. Despite this warning, it is natural for patients to do just that. To illustrate the problem in doing so, an example is in order: Suppose 10 patients enroll for treatment at Clinic A and all undergo IVF, with 7 being successful. Clinic A can boast a 70% success rate. Now suppose that those same 10 patients had enrolled instead in Clinic B, and that Clinic B takes a more conservative approach to using IVF. In Clinic B, only 5 patients undergo IVF, with more traditional treatment given to the remaining 5 patients. Now supposed that all 5 patients treated with the non-IVF approach conceive, but only 2 of the 5 who undergo IVF conceive. Although 7 of 10 patients are pregnant at Clinic B, the “success rate of Clinic B is only reportable as 40%. Because the focus is only on IVF outcomes, Clinic A has a “success rate” that is 30% higher than Clinic B. (Indeed, one could argue that it is 75% higher than Clinic B, because 70% as an absolute number is 75% (30/40) higher than 40%.) Yet, the actual number of patients who are successful is identical in both programs! Consumers who rate Clinic A as the better place for treatment have surely been misled. This is just one of many potential problems in using IVF statistics as the sole measure of a program’s quality. All consumers and patients should be aware that are many other factors that go into the quality assessment of fertility practices. If you are a patient undergoing active assessment or treatment, you should feel comfortable in discussing the quality measures that are important to you.

Success Factors in ART

There is little doubt that the woman’s age at the time of treatment is one of the most significant and predictable factors for success with ART. As age increases, a significant decline in pregnancy rates is seen. More than likely, this is a direct consequence of a decline in oocyte (egg) quality as the ovaries age. It should be noted that younger women may also be found to have diminished egg quality – so called diminished ovarian reserve – and that this will impact her chance of success with ART as well as her expected time frame to achieve a pregnancy independent of the reason for which ART has been recommended.

Embryo quality is yet another factor which may influence pregnancy rate. As a general rule, the better the quality of the embryos replaced, the higher the chance that at least one will implant in the uterus. Embryo quality at GENESIS is assessed at different stages of IVF using the visual inspection of the embryos at either the cleavage stage or the blastocyst stage. The criteria used to assess embryo quality are usually based on the cell morphology, or appearance, which in the cleavage stage (usually 3 days from egg retrieval) will include cell (blastomere) number, size, shape and degree of fragmentation. At the blastocyst stage (usually 5 days from egg retrieval) the level of expansion of the embryo as well as the appearance of different components, the inner cell mass (the precursor of the fetus) and the trophectoderm (precursor of the placenta and membranes.)  A different and sometimes more accurate way of assessing embryo quality is by genetic testing (preimplantation genetic screening).

Our most recent SART statistics are in the link above and demonstrate our success in achieving excellent clinical pregnancy rates per embryo transfer procedure. Patients should be aware that the comparison of clinic success rates may not be meaningful because patient medical characteristics, treatment approaches, and entry criteria for ART may vary from clinic to clinic. The prevention of high order pregnancies (triplets or more) is a complication of ART that we take very seriously at GENESIS. As such, we make every effort to follow the guidelines issued by the ASRM to limit the number of embryos transferred. Whenever clinically indicated, we recommend transfer of a single embryo so that multifetal pregnancy can be avoided. It is important to remember that the statistics only show live births data; they tell us nothing about the health of the children born as a result of ART. Responsible practitioners will sacrifice a few percentage points in statistics if that means fewer twins and triplets, because the healthiest pregnancies usually come with one baby at a time.

It is worth mentioning that, at GENESIS, we make judicious use of both cleavage stage and blastocyst transfer. This makes our statistical basis different than at programs where embryo transfer is done only at the blastocyst stage. The reason for this is that, at such programs, patients whose embryos do not develop to blastocyst stage will often not undergo embryo transfer at all, so they drop out of the live births per embryo transfer statistic, which is the most important statistic of all in ART. By eliminating such patients from this statistical denominator, the percentage of live births will automatically rise. Every program is free to choose what techniques work best for their patients, and there is nothing deceptive about reporting statistics that are in fact accurate. But patients should be aware that neither the ASRM nor the CDC has come up with a way to account for such variations in practice, which clearly impact on the data they present. Hence, we again emphasize that comparison of clinic success rates may not be meaningful because patient medical characteristics, treatment approaches, and entry criteria for ART may vary from clinic to clinic.