Understanding Stats:

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Understanding “Success” Statistics of an IVF Program

The most common question that I get from couples contemplating IVF is the “success statistics” of any IVF Program. Because a patient has to wait until all of the women in a various time period have given birth, the most recent available statistics posted by a program are generally at least one- if not two-years old. We provide our patients (or prospective patients) with tabulations of our “outcome” statistics, but we believe it is critical that patients be given the information to understand them. It is important to remember that “success statistics” represent an average result- they reflect the experience of the program with groups of patients. While such statistics do not necessarily reflect what your experience will be, they are a means of evaluating a specific program’s experience.

In reviewing success statistics, you should be aware of the meaning of the various “percentages” that are utilized to express them. “Percentages” of success represent a fraction, where the numerator (the top number) represents one group of patients who have achieved a successful stage of IVF therapy, and the denominator (the bottom number) represents the entire group of patients who underwent that particular treatment. When you divide the numerator by the denominator (and then multiply that by 100), you will arrive at a percentage. Obviously, choosing different numerators and different denominators can vastly change the percentages. In assisted reproductive technology (ART) programs, you will commonly see percentages that range wildly from as low as 10 or 20% all the way up to 80%. Many times this is due to the fact that those percentages are being generated from different numerators (stages of treatment) and denominators (the number of all patients who experienced that treatment). Anytime you read a percentage from an ART program it is important to know exactly what defines the numerator and the denominator.

Terminology

In order to understand the percentages that are provided, there are definitions that you should be aware of:

Initiated cycle: means that medication was initiated to stimulate the ovaries. Certainly, not all women who undergo stimulation will produce sufficient follicles. Where there is an inadequate response, the cycle will be “cancelled”.

Retrieval (Egg Retrieval): means that follicles were aspirated from the ovary to get eggs for fertilization.

Transfer (ET): means that embryos have been transferred into the uterus.

Clinical Pregnancy: means a gestational sac is visualized in the uterus (using ultrasound)

Using these definitions, there are a number of ways to express the pregnancy rates of any IVF Program

Pregnancy per Cycle initiated: this is a percentage which reflects the number of clinical pregnancies achieved, divided by the number of women who were given medication for ovulation induction.

Pregnancy per Retrieval: this is a percentage which reflects the number of clinical pregnancies, divided by the number of women who went through an egg retrieval.

Pregnancy per Transfer: this is a percentage which reflects the number of clinical pregnancies, divided by the number of women who went through embryo transfer.

National Report for ART programs

The Centers for Disease Control and the Society of Assisted Reproductive Technologies [SART] have generated a national report for all ART programs across the nation. The delivery rate per initiated cycle is reported to them and represents the babies delivered (counting a multiple birth as one delivery), divided by the entire number of women who were started on an IVF cycle started through the administration of medication. The most important section of the CDC/SART publication reports the average pregnancy rate for each age group for every IVF program throughout the country. As do most other IVF programs, we routinely submit our annual IVF treatment results to SART and this information is complied and published by the Centers for Disease Control and is available online (www.cdc.gov) for public review. Unfortunately, the process of reporting involves an inherent 2 to 3 year lag from the time of report to actual publication. While this delay is unavoidable, we have always felt that this leaves patients at a disadvantage since they must rely on “old” data to help them make critical decisions as to where to currently seek IVF treatment ART represent a rapidly advancing field of medical science. Changes in the staff or management of an IVF program that may impact results can take several years before they are reflected in the published success statistics. Newer programs (like VCRM) that currently achieve impressive success for their patients may remain undiscovered secrets, while formerly world-class programs may enjoy the benefits of their prior reputation for several years before the published statistics “catch up” with their current level of performance. Also bear in mind that newer programs (like VCRM) see a large number of patients who have failed in other programs or are considered unlikely to succeed, which negatively impacts our overall success rates. We are very proud that we continue to achieve such success with patients that many programs “reject”. Therefore, a “head-to-head” comparison between programs is not quite appropriate since the patient “mix” is not comparable among different programs. The next section deals with the factors that significantly impact your chances at getting pregnant with ART.

Success Factors

Age: There is no doubt that age is the single most important factor in determining your chance of achieving a successful conception through IVF. As the egg ages, it undergoes changes that render it less and less fertile as a woman advances through her 30’s and 40’s. As a woman’s age advances, her chance of conceiving through IVF decreases. Furthermore, her risk of early pregnancy loss increases during this same time period, mainly related to the increasing frequency of chromosomal abnormalities within the egg, and the resulting developing embryo.

Day3 FSH: Day 3 follicle-stimulating hormone (FSH) levels are also critically important in evaluating your potential for successful conception in an assisted reproductive technology program (see the section entitled “What is ovarian reserve and how does it impact my fertility”). This blood test is typically drawn on the third day of a woman’s menstrual cycle. Day 3 FSH levels have been shown to be an incredibly accurate predictor of IVF success, independent of age. Essentially, an elevated Day 3 FSH value indicates a very poor prognosis for conception through IVF, and a high risk of pregnancy loss should the rare conception occur. Unfortunately, if you ever exhibit an elevated FSH value, having a normal value at a later time does not favorably change this prognosis. Every IVF program establishes a “threshold” FSH value unique to their laboratory, above which pregnancies are very rarely conceived despite great effort and repeated IVF attempts. Prior to initiation of any IVF cycle, Day 3 FSH values are evaluated. Many factors can artificially depress FSH values, but only diminished ovarian fertility reserve can cause an elevated FSH level. Egg donation is generally recommended as the most potentially successful treatment option in the setting of elevated FSH levels, especially when associated with age beyond 35.

Clomiphene Citrate Challenge Test (CCCT): The clomiphene citrate challenge test can also be used to determine the extent of your ovarian fertility reserve. This test was designed to “unmask” undiagnosed cases of diminished ovarian reserve when Day 3 FSH values are apparently normal – the equivalent of a “stress test” for the ovaries. During the CCCT, a Day 3 FSH value is assessed. If normal, 100 mg/day of clomiphene citrate (Clomid, Serophene) is administered from days 5-9 of your menstrual cycle. An FSH level is then assessed on Day 10. If either the Day 3 or Day 10 FSH value is elevated, the test is considered abnormal and predicts a poor prognosis for IVF outcome.