Type of ART used
This section gives the breakdown of ART cycle types that each clinic performed using fresh nondonor eggs or embryos (IVF, GIFT, ZIFT, or combinations thereof). It also lists the percentage of procedures that involved intracytoplasmic sperm injection (ICSI), which was not performed by all clinics in 2002; the percentage of cycles that were unstimulated; and the percentage of cycles that used a gestational carrier. (See Glossary for definitions of IVF, GIFT, ZIFT, ICSI, and gestational carrier.)
ART patient diagnosis
Consumers may want to know what percentage of a particular clinic’s patients have the same diagnosis as they do. (See Glossary for definitions of diagnoses.) In addition, patients’ diagnoses may affect a clinic’s success rates. However, the use of these diagnostic categories may vary somewhat from clinic to clinic.
To have success rates published in the annual report, a clinic’s medical director must verify the accuracy of the tabulated success rates. The name of the individual who verified the clinic’s data is shown.
Success rates by type of cycle
Success rates are given for the three categories of cycles described in 4A–C below: cycles using fresh embryos from nondonor eggs, cycles using frozen embryos from nondonor eggs, and cycles using donor eggs. The ART success rates shown were calculated based on data from all ART cycle types (IVF, both with and without ICSI; GIFT; and ZIFT). Data from these procedures were combined because there was little difference in success rates when we examined each type of ART procedure separately.
The success rates indicate the average chance of success for the given procedure at the clinic in 2002 for each of four age groups. Success rates are calculated as the percentage of cycles started, egg retrievals, or embryo transfers that resulted in either pregnancies or live births at the ART clinic in 2002. For example, if a clinic started a total of 50 cycles in 2002 and these resulted in 15 live births, the average success rate for cycles started at that clinic would be
15 (births) ÷ 50 (cycles) = 0.3 or 30%.
Thus, the success rate at that clinic in 2002 was 30%, meaning that 30% of cycles started that year resulted in a live birth.
Success rate calculations are very unstable if they are based on a small number of cycles. Therefore, when fewer than 20 cycles are reported in a given category, the rates are shown as fractions rather than percentages. For example, the sample clinic carried out only 19 fresh-embryo cycles using nondonor eggs among women aged 41–42 years. Of these 19 cycles, 2—or 10%—were successful. However, because of the small number of cycles, 10% is not a statistically reliable success rate, so the success rate is presented as 2 / 19, meaning 2 out of 19.
Cycles using fresh embryos from nondonor eggs
This section includes IVF, ICSI, GIFT, and ZIFT cycles that used a woman’s own eggs. Cycles that used frozen embryos or donor eggs or embryos are not included here.
- Percentage of cycles resulting in pregnancies
(Number of pregnancies divided by number of cycles started, expressed as a percentage of cycles)
A stimulated cycle is started when a woman begins taking fertility drugs; an unstimulated cycle is started when egg production begins being monitored. The number of cycles that a clinic starts is not the same as the number of patients that it treats because some women start more than one cycle in a year. Because some pregnancies end in a miscarriage, induced abortion, or stillbirth, this rate is usually higher than the live birth rate.
- Percentage of cycles resulting in live births
(Number of live births divided by number of cycles started, expressed as a percentage of cycles)
This number represents the cycles that resulted in a live birth out of all ART cycles started. One live birth may include one or more children born alive; that is, a multiple-infant birth (e.g., twins, triplets) is counted as one live birth.
- Percentage of retrievals resulting in live births
Number of live births divided by number of egg retrieval procedures, expressed as a percentage of retrievals)
This number represents the cycles that resulted in a live birth out of all cycles in which an egg retrieval was performed. The number of egg retrievals a clinic performs often is smaller than the number of cycles started because some cycles are canceled before the woman has an egg retrieved. As a result, this rate is usually higher than the live births per cycle started rate. Cycles are canceled for many reasons: eggs may not develop, the patient may become ill, or the patient may choose to stop treatment (see Figure 4).
- Percentage of transfers resulting in live births
(Number of live births divided by number of embryo transfer procedures, expressed as a percentage of transfers)
This number represents the cycles that resulted in a live birth out of all cycles in which one or more embryos were transferred into the woman’s uterus or, in the case of GIFT and ZIFT, egg and sperm or embryos were transferred into the woman’s fallopian tubes. A clinic may carry out more egg retrievals than embryo transfers because not every retrieval results in egg fertilization and embryo transfer. For this reason, live birth rates based on transfers generally will be higher than those reported for egg retrievals and for cycles started.
- Percentage of transfers resulting in singleton live births
(Number of singleton live births divided by number of embryo transfer procedures, expressed as a percentage of transfers)
This number represents the cycles that resulted in the birth of a single infant out of all cycles in which one or more embryos were transferred into the woman’s uterus or, in the case of GIFT and ZIFT, egg and sperm or embryos were transferred into the woman’s fallopian tubes. Singleton births have a much lower risk than multiple-infant births for adverse infant health outcomes, including prematurity, low birth weight, disability, and death.
- Percentage of cancellations
(Number of cycles canceled divided by the total number of cycles, expressed as a percentage of cycles)
This number refers to the cycles that were stopped before an egg was retrieved. A cycle may be canceled if a woman’s ovaries do not respond to fertility medications and thus do not produce a sufficient number of follicles. Cycles also may be canceled because of illness or other medical or personal reasons.
- Average number of embryos transferred
(Average number of embryos per embryo transfer procedure)
The average number of embryos transferred varies from clinic to clinic. The American Society for Reproductive Medicine (ASRM)* and the Society for Assisted Reproductive Technology (SART)* have practice guidelines that address this issue.
- Percentage of pregnancies with twins
(Number of pregnancies with two fetuses divided by the total number of pregnancies, expressed as a percentage of pregnancies)
A pregnancy with two fetuses is counted as one pregnancy.
- Percentage of pregnancies with triplets or more
(Number of pregnancies with three or more fetuses divided by the total number of pregnancies, expressed as a percentage of pregnancies)
Pregnancies with multiple fetuses can be associated with increased risk for mothers and babies (e.g., higher rates of caesarean section, prematurity, low birth weight, infant death) and the possibility of multifetal reduction.
A pregnancy with three or more fetuses is counted as one pregnancy.
- Percentage of live births having multiple infants
(Number of deliveries resulting in a birth of more than one infant divided by the number of live births, expressed as a percentage of live births)
A delivery of one or more babies is counted as one live birth.
Cycles using frozen embryos from nondonor eggs
Frozen (cryopreserved) embryo cycles are those in which previously frozen embryos are thawed and then transferred. Because frozen-embryo cycles use embryos formed from a previous stimulated cycle, no stimulation or retrieval is involved. As a result, these cycles usually are less expensive and less invasive than cycles using fresh embryos. In addition, freezing some of the embryos from a retrieval procedure may increase a woman’s overall chances of having a child from a single retrieval.
Cycles using donor eggs
Success rates are presented separately for cycles using fresh donor eggs or embryos and those using frozen donor embryos. Older women, women with premature ovarian failure (early menopause), women whose ovaries have been removed, and women with a genetic concern about using their own eggs may consider using eggs that are donated by a young, healthy woman. Embryos donated by couples who previously had ART also may be available. Many clinics provide services for donor egg and embryo cycles. For these cycle types, results from women in all age groups (including older than 42) are reported together because previous data show that patient age does not affect success rates with donor eggs (see Figures 36 and 37).
Age of woman
Because a woman’s fertility declines with age, clinics report lower success rates for older women attempting to become pregnant with their own eggs. For this reason, rates for women using nondonor eggs or embryos are reported separately for women younger than age 35, for women 35–37, for women 38–40, and for women 41–42. Clinic-specific outcome rates are not shown for women older than 42 who undergo ART using their own eggs because the number of women in this age group at each clinic is small; therefore, a calculation of the live birth rate in older age groups may not be meaningful. Readers are encouraged to review national outcomes for these age groups. The sample clinic table illustrates the decline in ART success rates among older women. For example, for cycles that used fresh embryos from nondonor eggs, the percentage of cycles resulting in live births among women younger than 35 was 37.4%, whereas the percentage of cycles resulting in live births among women aged 38–40 was 20.6%.
The tables show a range, called the 95% confidence interval, that conveys the reliability of a clinic’s demonstrated success rate. This range is calculated only if 20 or more cycles are reported in an age category. (When fewer than 20 cycles are reported in a given category, success rates are shown as fractions rather than percentages; see paragraph 4, Success Rates by Type of Cycle.) In general, the more cycles that a clinic performs, the narrower the range. A narrow range means we are more confident that a clinic would have a similar success rate if it treated other similar groups of patients under similar clinical conditions. On the other hand, a wide range tells us that a clinic’s success rate is more likely to vary under similar circumstances because we had less information (fewer cycles) on which to base our estimates. Even though one clinic’s success rate may appear higher than another’s based on the confidence intervals, these confidence intervals are only one indication that the success rate may be better. Other factors also must be considered when comparing rates from two clinics. For example, some clinics see more than the average number of patients with difficult infertility problems, whereas others discourage patients with a low probability of success. For more information, see important factors to consider when using the tables to assess a clinic.
See Appendix A for a more detailed explanation and examples of confidence intervals.
Clinic services and profile
Further information on laboratory accreditation is provided in Appendix C.