How to Interpret ART Success Rates

Interpreting success rates

Patients using their own eggs

Success rates for patients using their own eggs are shown per intended retrieval, per actual retrieval, and per transfer.

An ART cycle starts when a woman begins taking fertility drugs or having her ovaries monitored for follicle production with the plan to retrieve eggs (intended retrieval). If eggs are produced, the cycle progresses to egg retrieval, in which at least one egg is retrieved (actual retrieval).

Eggs are then combined with sperm in the laboratory. If fertilization is successful, at least one embryo may be selected for transfer. The embryos may be transferred to the patient or to a gestational carrier. If the embryo transfer results in implantation, the cycle may progress to clinical pregnancy and, possibly, a live-birth delivery.

Cumulative success rates for patients using their own eggs are shown based on egg retrievals performed in the prior year and all transfers of embryos that occurred within 1 year after an egg retrieval. For clinics that did not report data from the prior year, cumulative success rates for patients using their own eggs cannot be calculated.

Patients using donor eggs or embryos

Success rates for patients using donor eggs, donor embryos, or donated embryos from patients who previously used ART are shown per transfer. Success rates are presented by the types of eggs and embryos used in the transfer. Success rates are not presented by age group because previous data show that an intended parent's age does not substantially affect success when using donor eggs or embryos. Rates for patients using donor eggs or embryos are noncumulative. They are based on transfers performed that year.

Considerations when interpreting success rates

Many people considering ART may want to use the clinic success rates information on the ART Success Rates web page to find the "best" clinic. However, comparisons between clinics should be made with caution.

Many factors contribute to the success of an ART procedure. Comparison of success rates across clinics may not be meaningful. Clinics may have different rates because they have different patient populations or ART treatment methods. Comparing clinic-specific success rates to national rates should also be interpreted with caution for this reason.

Clinic success rates do not reflect any one patient's chance of success. Patients should talk with a doctor to understand their own chance of success based on their characteristics.

Important factors to consider when interpreting clinic success rates:

• Data are from ART cycles performed more than 1 year ago.

Before success rates can be calculated, the following must occur: (1) ART treatments need to be completed; (2) completed cycles need to be followed up to determine whether a birth occurred; (3) data need to be collected, reported, cleaned, and analyzed; and (4) data need to be prepared for publication.

Many factors that contribute to a clinic's success rates can change after the cycles included in the data presented here were performed. Personnel may be different, and equipment and training may or may not have been updated. As a result, the published success rates may not necessarily represent current practice.

• Success rates may vary between clinics based on many different factors.

Some factors are related to the training and experience of the fertility clinic and laboratory professionals and the quality of services they provide. Other factors are related to the patients themselves, such as their age, the quality of their eggs and sperm, the cause of their infertility, and genetic factors. Some clinics may be more willing than others to accept patients with low chances of success, or they may specialize in ART treatments that attract particular types of patients. Others may discourage patients with low chances of success from pursuing ART treatments, or they may encourage them to use donor eggs, which can result in higher success rates among some patients. CDC does not collect information on clinic-specific patient selection practices.

• Success rates may vary from year to year.

A clinic's success rates may vary from year to year, even if all factors remain the same. The more cycles that a clinic carries out, the less the rate is likely to vary. Clinics that perform fewer cycles are likely to have more variability in success rates from year to year. As an extreme example, if a clinic reports only one ART cycle in a given category, as is sometimes the case in the data presented here, the clinic's success rate in that category would be either 0% or 100%.

Please contact us with any questions or suggestions at ARTinfo@cdc.gov.