Why is the report of 1997 success rates being published in now?
Before success rates based on live births can be calculated, every ART pregnancy must be followed up to determine if a birth occurred. Thus the earliest that clinics can report annual data is late in the year after ART treatment was initiated (9 months past year-end, when all the births have occurred). Accordingly, the results of all cycles initiated in 1997 were not known until October 1998. After ART outcomes were known, the following steps had to be completed before the report could be published:
- Clinics entered their data into an electronic data collection system and verified the data’s accuracy before sending the data to SART.
- SART compiled a national data set from the data submitted by individual clinics.
- CDC randomly selected a percentage of the reporting clinics for on-site quality control visits by SART validation teams, who checked the submitted data against the information in the medical records to be sure they corresponded.
- CDC data analysts did comprehensive checks of the numbers reported for every clinic.
- Clinic tables, national figures, and accompanying text in both the printed and Web site versions were compiled and laid out.
- CDC, SART/ASRM, and RESOLVE reviewed and approved the report.
These steps are time-consuming but essential to ensure that the report provides the public with correct information and does not misrepresent any clinic’s success rates.
Which clinics are represented in this report?
The data in both the national report and the individual fertility clinic reports come from 335 fertility clinics that provided and verified information about the outcomes of the ART cycles started in their clinics in 1997. A few clinics that are now independent were operating as part of other clinics in 1997 and accordingly are not listed separately in the report.
Although we believe that almost all clinics that provided ART services in the United States throughout 1997 are represented in this report, data for a few clinics or practitioners have not been included because they either were not in operation throughout 1997 or did not report as required. Clinics and practitioners known to have been in operation throughout 1997 that did not report and verify their data are listed in this report as non-reporters, as required by law.
What quality control steps are used to ensure data accuracy?
To have their success rates published in this annual report, clinics have to submit their data in time for analysis, and the clinics’ medical directors have to verify that the tabulated success rates are accurate. After the data have been verified, a quality control process called validation begins. This year, 30 of the 335 reporting clinics were randomly selected for site visits. Two members of the SART Validation Committee visited these clinics and compared medical records data on 50 randomly selected cycles with the data submitted for the report. In almost all cases, data on pregnancies and births in the medical records were consistent with reported data. Validation primarily helps to ensure that clinics are being careful to submit accurate data. It also serves to identify any systematic problems that could cause data collection to be inconsistent or incomplete.
Although SART compares medical records with data submitted for this report, the validation process does not include any assessment of clinical practice or overall record keeping.
Does this report include all ART cycles performed by the reporting clinics?
A small number of ART cycles are not included in the national data. These cycles are mainly in one of the following two categories:
- Surrogate or gestational carrier cycles, in which a woman other than the intended mother received the embryo transfer. In 1997, 600 such cycles were reported to CDC; the overall success rate of cycles using gestational carriers was 31.2%.
- Cycles in which a new treatment procedure (e.g., cytoplasmic egg transfer) was being evaluated. Only 40 ART cycles fell into this category in 1997.
If a woman has had more than one ART treatment cycle, how is the success rate calculated?
As required by law, this report presents ART success rates in terms of cycles started each year rather than in terms of women. (A cycle starts when a woman begins taking fertility drugs or having her ovaries monitored for follicle production.) Therefore, women who had more than one ART cycle started in 1997 are represented in multiple cycles. Success rates cannot be calculated on a “per woman” basis because women’s names are not reported to SART and CDC.
Assisted
Reproductive Technology
Data
provided by U.S. clinics that use assisted reproductive technology (ART)
to treat infertility are a rich source of information about the factors
that contribute to a successful ART treatment: the delivery of a
live-born infant. Pooling the data from all reporting clinics provides
an overall national picture that could not be obtained by examining data
from an individual clinic.
A woman’s chances of having a pregnancy and a live birth by using ART are influenced by many factors, some of which (e.g., the woman’s age and the cause of infertility) are outside a clinic’s control. Because the national data set includes information on many of these factors, it can give potential ART users an idea of their average chances of success. Average chances, however, do not necessarily apply to a particular individual or couple. People considering ART should consult their physician to discuss all the factors that apply in their particular case.
The data for this national report come from the 335 fertility clinics in operation in 1997 that provided and verified data on the outcomes of all ART cycles started in their clinics. ART cycles performed at the reporting clinics in 1997 resulted in 17,054 deliveries of one or more living infants and 24,582 babies.
The national report consists of graphs and charts that use 1997 data to answer specific questions related to ART success rates. These figures are organized according to the type of ART procedure used. Some ART procedures use a woman’s own eggs, and others use donated eggs or embryos. (Although sperm used to create an embryo may also be either from a woman’s partner or from a sperm donor, this report is organized according to the source of the egg.) In some procedures, the embryos that develop are transferred back to the woman (fresh transfer); in others, the embryos are frozen (cryopreserved) for transfer at a later date. This report includes data on frozen embryos that were thawed and transferred in 1997.
The national report has four sections:
- Section 1 (Figures 1 and 2) presents information from all ART procedures reported.
- Section 2 (Figures 3 through 17) presents information on the 55,002 ART cycles that used only fresh embryos from non-donor eggs or, in a few cases, a mixture of fresh and frozen embryos from non-donor eggs.
- Section 3 (Figure 18) presents information on the ART cycles that used only frozen embryos (10,181 cycles resulting in 9,165 transfers).
- Section 4 (Figures 19 and 20) presents information on the ART cycles that used only donated eggs or embryos (6,643 cycles resulting in 5,980 transfers).
Check out the 1997 national summary table, which is based on data from all clinics included in this report. An explanation of how to read these tables is also included.
Most
IVF, GIFT, and ZIFT cycles used fresh, nondonor eggs or embryos.
An
ART cycle is started when a woman begins taking medication to
stimulate the ovaries to develop eggs or, if no drugs are given, when
the woman begins having her ovaries monitored (using ultrasound or blood
tests) for natural egg production. 
Figure
4 presents 1997 ART cycles using fresh, nondonor eggs or embryos
according to the age of the woman who had the procedure. About 70% of
these cycles were among women aged 30–39. Because very few women
younger than age 22 used ART and very few women older than age 47 used
ART with their own eggs, those cycles are not included in the figure.
Most
of these women (78%) had no previous births; however, they may have had
a pregnancy that resulted in a miscarriage or a therapeutic abortion.
Sixteen percent reported one previous birth, and 6% reported two or
more. However, we do not know how many of these children were conceived
naturally and how many by an ART procedure. These data nonetheless point
out that women who have previously had children can face infertility
problems. These infertility problems can include infertility of a new
partner.
Figure
6 shows the primary diagnoses reported for infertility among couples who
had an ART procedure in 1997. Although some couples have more than one
cause of infertility, only one is reported as primary. In addition,
diagnostic procedures and categories may vary from one clinic to
another, so the categorization may be inexact. 
Several
measures can be used to assess ART success rates. Each provides slightly
different information about this complex process. Figure 7 shows ART
success rates using four different ways of measuring ART success.
Age-specific success rates using each of these measures are in the
National Table. 
Live
birth rates vary by type of ART procedure used. Figure 8 shows the
percentage of egg retrievals in 1997 that used a particular type of ART
procedure and resulted in a live birth. Because the same patterns were
seen among all age groups, results are given for all age groups
combined. GIFT had a slightly higher success rate than IVF. However,
some women with tubal infertility are not suitable candidates for GIFT
and ZIFT. In addition, GIFT and ZIFT are more invasive procedures than
IVF because they involve inserting a laparoscope into a woman’s
abdomen to transfer the embryos or gametes into the fallopian tubes. In
contrast, IVF involves transferring embryos into a woman’s uterus
through the cervix without surgery. 
Figure
10 shows the outcomes of the ART cycles that resulted in pregnancies in
1997 (see Figure 9). Approximately 81% resulted in a live birth
(50.1% in a single birth and 31.2% in a multiple birth). Thus, 38% of
all ART births were multiple births, compared with less than 3% of
births in the general population. Multiple births are associated with
greater problems for both mothers and infants. Approximately 17% of
pregnancies resulted in an adverse outcome (miscarriage, ectopic
pregnancy, induced abortion, or stillbirth), and the outcomes of about
2% of pregnancies were unknown.
A
woman’s age is the most important factor affecting the chances of a
live birth when her own eggs are used. Figure 11 shows both the
pregnancy and live birth rates for women of different ages who had ART
procedures in 1997. Among women in their twenties, both pregnancy and
live birth rates were relatively stable; however, both rates declined
sharply from the mid-thirties onward as fertility declined with age.
Figure
12 shows that a woman’s chances of success using ART (with her own
eggs) decrease at every stage of ART as her age increases. 
Figure
13 shows the relationship between the success of an ART cycle performed
in 1997 and the history of previous births to the woman who had the
treatment. Previous live births were conceived naturally in some cases
and through ART in others. In all age groups, women who had not had a
previous live birth were less likely to have a live birth by using ART.
Figure
14 shows the percentage of live births after an ART procedure according
to the primary cause of infertility. (See the glossary for an
explanation of the diagnoses.) The success rates varied little among
most of the different diagnoses; most were near the overall national
success rate of 24.0%. However, the use of these diagnostic categories
may vary from clinic to clinic, and the definitions are imprecise.
The
relationships between number of embryos transferred, success rates, and
multiple births are complicated by several factors. Thus, the
relationships shown in this figure do not hold for all women. A more
detailed CDC report that discusses how age and embryo quality may affect
the relationships between the number of embryos transferred, live birth
rates, and multiple birth rates has been published in a separate journal
article [Journal of the American Medical Association
1999;282(19):1832-1838.]
In
1997, approximately 30% of fresh, nondonor ART cycles used ICSI (intracytoplasmic
sperm injection, a procedure in which a single sperm is injected
directly into an egg), most often to overcome problems with sperm
function or motility. Figure 16 compares the success rates for ART
procedures involving ICSI with those not involving ICSI among couples
with male factor infertility as the primary diagnosis. Because ICSI can
be performed only when at least one egg has been retrieved, only the
live birth per retrieval rate and the live birth per transfer rate are
compared. In 1997, success rates per retrieval were slightly higher when
ICSI was used, indicating that ICSI may improve the chances of
fertilization among couples with male factor infertility. The similarity
in success rates for live births per transfer with and without ICSI
shows that once the egg was fertilized, ICSI did not affect the success
rate.
Fertility
clinics in the United States vary in the number of ART procedures that
they carry out every year. In 1997, success rates tended to be slightly
higher among clinics that performed more cycles. In Figure 17, clinics
are divided into four equal groups (called quartiles) based on the size
of the clinic as determined by the number of cycles it carried out. The
percentages for each quartile
Approximately
14% of all ART cycles performed in 1997, or 10,181 cycles, used only frozen
embryos. Figure 18 compares the success rates for frozen embryos with the rate
for fresh embryos. Some embryos do not survive the freezing or thawing process.
Thus, the live birth per thaw rate, which takes into account all embryos frozen,
is usually lower than the live birth per transfer rate. In 1997, the live birth
per thaw and live birth per transfer rates for frozen embryos were lower than
the live birth per transfer rate for fresh embryos. However, cycles that use
frozen embryos are both less expensive and less invasive than fresh cycles
because the woman does not have to go through the fertility drug stimulation and
egg retrieval process again.
As
shown in Figure 12, eggs produced by women in older age groups form embryos that
are less likely to implant and more likely to miscarry if they do implant. As a
result, ART using donor eggs is much more common among older women than among
younger women. Donor eggs were used in approximately 9% of all ART cycles
carried out in 1997, or 6,643 cycles. Figure 19 shows the percentage of ART
cycles using donor eggs in 1997 according to the woman’s age. Donor eggs were
used in less than 5% of cycles among women younger than age 37. The percentage
of cycles carried out with donor eggs then increased sharply. Among women older
than age 46, more than 70% of all ART cycles used donor eggs.
Figure
20 compares success rates for ART using donor eggs with those for ART using a
woman’s own eggs among women of different ages. The likelihood of a fertilized
egg implanting is related to the age of the woman who produced the egg. Egg
donors are typically in their twenties or early thirties. Thus, the live birth
per transfer rate for cycles using embryos from donor eggs varies only slightly
across all age groups. In contrast, this rate for cycles using embryos from the
woman’s own eggs declines steadily as women get older.
