IVF success rates essentially represent the pregnancy rates associated with undergoing IVF. There are several ways to calculate IVF success rates, but all IVF success rates are calculated by dividing the number of positive outcomes (i.e., number of pregnancies) by the number of procedures performed (i.e., number of embryo transfers).
The important thing to remember is that the center with the highest pregnancy rates may not be the best center for every patient. This is counter-intuitive – let me explain. Caution should be exercised when looking at a center’s pregnancy rates because any center can manipulate their numbers so that their pregnancy rates look higher than other centers, which then gives that practice a market advantage over other practices. Unfortunately, we see this frequently where some centers tout a 100% pregnancy rate!

How are IVF success rates calculated?

The major types of IVF success rates are the positive pregnancy rate, the clinical pregnancy rate and the live birth rate.

The positive pregnancy rate is the number of positive pregnancy tests divided by the number of IVF cycles initiated or completed, or the number of embryo transfers. Clinical pregnancy rate refers to the number of pregnancies seen on a sonogram. This is used most often when the number of live births is not yet available. Because a pregnancy takes about 40 weeks to reach full term, IVF centers that want to publish their pregnancy rates before all their patients reach that end point must use clinical pregnancy rate when reporting their outcomes.

However, patients are probably most interested in the live birth rate, the likelihood of having a “take-home baby” after an IVF cycle. Live birth rate tracks each IVF pregnancy all the way to delivery. This number tends to be lower than the clinical pregnancy rate because of the incidence of miscarriage.

The CDC/SART publishes the live birth rate for its members every year. Unfortunately, it takes more than a year for the CDC/SART pregnancy rates to become available, raising the concern that the published data may be too old to be representative of an IVF center’s current performance. That being said, SART is the primary organization of professionals dedicated to the practice of IVF. Its mission is to establish and maintain standards of IVF so that a patient receives a high level of care. Ninety percent of IVF clinics report to SART. In the St. Louis region, SIRM-STL is only one of two clinics that currently report to SART. Other clinics, who choose not to do so, have little oversight and may give success rates that are not completely accurate.

How to Use IVF Success Rates to Find the “Right” IVF Center

When looking for an IVF center with which to work, many educated infertility patients look at each IVF center’s published IVF success rates. IVF pregnancy rates can and should play a role in selecting an IVF center. However, it is practically impossible to compare fertility centers by comparing their outcomes primarily because of patient selection bias, and possibly due to manipulations of outcome data reporting.

The problem of patient selection bias exists in other fields of medicine, especially in surgical specialties. For example, the government annually publishes mortality rates for coronary bypass surgeries. Interestingly, the highest mortality rates occur in some of the most advanced surgical units. This observation is thought to be due to the fact that these units accept and treat the most difficult cases. This is patient selection bias – the toughest cases are done in the best surgical units. Tough cases result in lower success.
The same can be true with IVF centers. In general, one can’t compare one clinic with another clinic because patient populations could vary. For example, let’s compare 2 different clinics – Clinic A versus Clinic B. Clinic A decides that they are only going to take the most favorable patients such young patients that have never gone through IVF. And Clinic B decides that they’ll treat everyone, regardless of their prognosis, including those that have failed at other places. Clinic A is likely to have higher success rates than Clinic B. In this scenario, it wouldn’t really be fair to compare Clinic A to Clinic B because they are treating entirely different types of patients. At SIRM-STL, we pride ourselves for having higher than national average success rates despite treating some of the most difficult of cases, including couples who have not been successful elsewhere.

This is an extremely important issue — the patient population directly impacts a center’s results. Selecting a fertility center or IVF program based on IVF pregnancy rates alone can be extremely misleading. And excessively high pregnancy rates should also be suspect.

Final thoughts

When you are trying to select an IVF center for your treatment, there are a few things to keep in mind.

  • Be sure you go to a clinic with fellowship-trained reproductive endocrinologists.
  • Choice of an IVF center should not be based on success rates alone – it should be based on a variety of other factors, such as the over-riding philosophy of the practice, how often you see your physician, how personalized is the care you will be receiving, and other patients’ experiences. Look at physician ratings (RateMD, etc.), the practice websites and Facebook pages to better gauge a practice. It is important that you feel comfortable moving forward with your treatment within the practice.
  • In general, beware of IVF centers with exceptionally high IVF success rates as these numbers can be manipulated.
  • Look at the center’s IVF success rates in their egg donor programs. Pregnancy rates in egg donor program are typically not influenced by patient selection. If a fertility center has a good IVF pregnancy rate in its egg donor program, the center is more likely to be skilled at IVF techniques.