A Numbers Game: Understanding Fertility Success Rates


If you’re considering fertility treatment, you’ve probably started investigating fertility clinics. One of the major factors many people consider is the clinics’ fertility success rates (these are an excellent tool in the assessment ‘tool kit’, but not the only aspect to consider when selecting the right clinic).

But these success rate numbers are not easy to understand, and different clinics report them in different ways. You may be comparing apples to oranges, or even to grapes! Here’s some basic information to help you use the data you’ll find on IVF success rates.

Where Do the Numbers Come From?

Assisted Reproductive Technology (ART) covers all fertility treatments in which a clinic handles both eggs and sperm, according to the Centers for Disease Control and Prevention (CDC.) That includes in vitro fertilization, but does not include artificial insemination—also known as intrauterine insemination, or IUI—or taking medications like Clomid to stimulate egg production if the eggs are not going to be retrieved for IVF.

CDC requires fertility centers to report their results in a lot of detail each year. The ART Success Rates Report provides an in-depth picture of the number of IVF cycles across the country and also has “success” data on individual clinics. Many infertility clinics post the data they report to the CDC on their websites. The most recent data is usually one and a half to two years old because of the time required to collect and report on a full year of procedures and results (live births.)

Complete information on any infertility clinic is available at www.cdc.gov .If a practice has been open less than two years, their data will not be filed on the CDC website. The Society for Reproductive Technology (SART) also produces a report that is released to the public www.sart.org. The report is released more quickly, usually one and half years after treatment is completed in a calendar year. Practices are not required to file their data with SART, so approximately 85% of all fertility centers report top SART.

Terms You Need to Know

You may see some or all of these terms on a fertility center’s website, or you may just see “fertility rate” or a summary. It’s important to look at the details and understand what they mean. Each term is another step in the process of IVF. Think of it as a funnel—unfortunately, everyone who begins the process will not make it all the way to a live delivery of a baby. The data is mostly depicted in percentage points. It may be helpful to understand that even if you don’t have any fertility issues, the chance of getting pregnant in any given ovulatory cycle is about 15 to 25 percent.

Initiated cycles means all the clinic’s attempts to induce ovulation (get the woman to produce eggs) so an IVF cycle can start. If ovulation induction does not work, due to the woman’s age or other issues, then cancellation of the cycle may occur before egg retrieval.

Egg retrievals refers to extracting the eggs from the ovarian follicles so the IVF lab can go on to the next step. After the eggs are retrieved and fertilized with sperm, embryos develop (again, if all goes well.) Then embryo transfer takes place. A clinical pregnancy means a pregnancy sac has been identified in the uterus, which means an embryo has implanted. The funnel continues to narrow, however, because it is possible to miscarry.

On average, about 25 percent of all recognized pregnancies (not just those from IVF) result in miscarriage. That’s why clinical pregnancy rate per embryo transfer may not be a relevant measure. Delivery rate, also known as live birth rate, measures percent of babies delivered. Delivery rate or live birth rate per egg retrieval shows the percentage of babies delivered from the total number of retrievals that took place. Delivery rate per embryo transfer is another measure of success.

Age, Number of Cycles and Multiples

If you get the complete report, there will be more tables, breaking down the data by age of the woman and by the number of cycles performed. This lets you evaluate the success rate based on the woman’s age, which is important for women over 35, and on the number of cycles. These are statistical indicators that may not fit for every patient. Your own results may be different due to your medical history or other factors.

Finally, take a look at the number of multiple pregnancies. A few clinics only transfer one embryo, but most will transfer two or three to increase your chances of having one “take” without doing more cycles. The percentage of multiple births is slightly higher with ART than without ART, but the percentage of “high multiples” (more than twins) is usually quite low. Most fertility specialists follow the guidelines on embryo transfer which were developed by the American Society for Reproductive Medicine (ASRM.) The guidelines benchmark the number transferred to the age of the patient and the stage of the embryo’s development.

Apples, Oranges and Grapes

Now that you understand the terms and have taken a look at the numbers, let’s talk about factors that may make the same measures not the same from one clinic to another. The CDC says: “Comparisons between clinics must be made with caution. Many factors contribute to the success of an ART procedure. Some factors are related to the training and experience of the ART clinic and laboratory professionals and the quality of services they provide. Other factors are related to the patients themselves, such as their age and the cause of their infertility. Some clinics may be more willing than others to accept patients with low chances of success or may specialize in various ART treatments that attract particular types of patients.”

So it’s important to look at more than the numbers. Consider your needs and circumstances when you’re deciding on a fertility clinic, as well as success rates.

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