Procedures and Success Rates
At the conclusion of this course the student will be have a basic understanding
of the Assisted Reproductive Technology, including IVF, GIFT and ZIFT, the
success rates and reasons therefore.
For many people who want to
start a family, the dream of having a child is not easily realized; about 15% of
women of childbearing age in the United States have received an infertility
service. Assisted reproductive technology (ART) has been used in the United
States since 1981 to help women become pregnant, most commonly through the
transfer of fertilized human eggs into a womans uterus. However, for many
people, deciding whether to undergo this expensive and time-consuming treatment
can be difficult.
The Society for Assisted
Reproductive Technology (SART), an organization of ART providers affiliated with
the American Society for Reproductive Medicine (ASRM), has been collecting data
and publishing annual reports of pregnancy success rates for fertility clinics
in the United States and Canada since 1989. In 1992, the U.S. Congress passed
the Fertility Clinic Success Rate and Certification Act, which requires the
Centers for Disease Control and Prevention (CDC) to publish pregnancy success
rates for ART procedures carried out in fertility clinics in the United
Success rates can be reported
in a variety of ways, and the statistical aspects of these rates can be
difficult to interpret. As a result, presenting information about ART success
rates is a complex task. This course has put the emphasis is on presenting the
information in an easily understandable form.
What is assisted reproductive technology (ART)?
definitions have been used for ART, the definition used in this
article is based on the 1992 law that requires CDC to publish this
report. According to this definition, ART includes all fertility
treatments in which both eggs and sperm are manipulated. In general,
ART involves surgically removing eggs from a womans ovaries,
combining them with sperm in the laboratory, and returning them to
the womans body or donating them to another woman. It does NOT
include procedures in which only sperm are manipulated (i.e.,
artificial insemination or intrauterine insemination) or procedures
in which a woman takes drugs only to stimulate egg production,
without the intention of having eggs retrieved. The types of ART
- IVF (in vitro
- GIFT (gamete
- ZIFT (zygote
These terms are
explained in Figure 1 and in the glossary.
In addition, ART
is often categorized according to whether the procedure used a womans
own eggs (nondonor) or eggs from another woman (donor) and according
to whether the embryos used were newly fertilized (fresh) or
previously fertilized, frozen, and then thawed (frozen).
many people in the United States have infertility problems?
The latest data
on infertility available at CDC are from the 1995 National Survey of
- Of the
approximately 60 million women of reproductive age in 1995,
about 1.2 million, or 2%, had had an infertility-related medical
appointment within the previous year, and an additional 13% had
received infertility services at some time in their lives.
(Infertility services include medical tests to diagnose
infertility, medical advice and treatments to help a woman
become pregnant, and services other than routine prenatal care
to prevent miscarriage.)
7% of married couples in which the woman was of reproductive age
(2.1 million couples) reported they had not used contraception
for 12 months and had not become pregnant.
the report of 1997 success rates being published in now?
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 datas accuracy before sending the data to SART.
- SART compiled a
national data set from the data submitted by individual
- 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
- CDC data
analysts did comprehensive checks of the numbers reported for
- 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 clinics
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
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.
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.
compares medical records with data submitted for this report, the
validation process does not include any assessment of clinical
practice or overall record keeping.
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
woman has had more than one ART treatment cycle, how is the success rate
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 womens
names are not reported to SART and CDC.
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 womans chances
of having a pregnancy and a live birth by using ART are influenced by
many factors, some of which (e.g., the womans age and the cause of
infertility) are outside a clinics 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
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
womans own eggs, and others use donated eggs or embryos. (Although
sperm used to create an embryo may also be either from a womans
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
The national report
has four sections:
- Section 1 (Figures
1 and 2) presents information from all ART procedures
- 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
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
What types of ART procedures were used in the United States in 1997?
A total of 71,826 ART cycles
were carried out in 1997 using one of the following procedures:
- IVF (in vitro
extracting a womans eggs, fertilizing the eggs in the laboratory, and
then transferring the resulting embryo(s) into the womans uterus through
- GIFT (gamete
intrafallopian transfer) involves
using a fiber-optic instrument called a laparoscope to guide the transfer of
unfertilized eggs and sperm (gametes) into the womans fallopian tubes
through small incisions in her abdomen.
- ZIFT (zygote
involves fertilizing a womans eggs in the laboratory and then using a
laparoscope to guide the transfer of the fertilized eggs (zygotes) into her
IVF, GIFT, and ZIFT cycles used fresh, nondonor eggs or embryos.
Where are ART clinics located?
ART clinics are located throughout the United States, the greatest number
of clinics is in the eastern United States. Most clinics are in or near major
cities. Figure 2 shows the location of the 335 reporting clinics. The fertility
clinic section of this report, arranged in alphabetical order by state, city,
and clinic, provides specific information on each of these clinics.
Figure 3 presents the
steps for a fresh, nondonor ART cycle and shows how ART users progressed
through these steps in 1997.
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.
If eggs are produced,
the cycle then progresses to egg retrieval, a surgical procedure
in which eggs are collected from a woman's ovaries.
Once retrieved, eggs
are combined with sperm in the laboratory. If fertilization is
successful, one or more of the resulting embryos are selected for transfer,
most often into a woman's uterus through the cervix (IVF).
If one or more of the
transferred embryos implants within the woman's uterus, the cycle then
progresses to clinical pregnancy.
pregnancy may progress to a live birth, the delivery of one or
more live-born infants. (A multiple birthtwins, triplets, or moreis
counted as one live birth.)
A cycle may be
discontinued at any step for specific medical reasons (e.g., no eggs are
produced or the embryo transfer was not successful) or by patient
are the ages of women
who have an ART procedure?
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 3039. 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.
many women who used
ART previously given birth?
Figure 5 shows the
number of previous children born to women who had an ART procedure in
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
are the causes of infertility
among couples who use ART?
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.
- Tubal factor
usually means that the womans fallopian tubes are blocked or
damaged, making it difficult for the egg to be fertilized or for an
embryo to travel to the uterus.
- Male factor
usually refers to a low sperm count or problems with sperm function
that make it difficult for a sperm to fertilize an egg under normal
involves the presence of tissue similar to the uterine lining in
abnormal locations. This condition can affect both egg fertilization
and embryo implantation.
dysfunction means that the ovaries are not producing eggs
normally or that egg production has diminished with age.
cause means that no cause of infertility was found in either the
woman or the man.
- Other causes
of infertility include immunological problems, chromosomal
abnormalities, cancer chemotherapy, and serious illnesses.
- Uterine factor
means a disorder of the uterus that results in reduced
How is the success
of an ART procedure measured?
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
- The pregnancy
per cycle rate refers to the percentage of ART cycles that
produced a pregnancy. This rate is higher than the live birth per
cycle rate because some pregnancies end in miscarriage, therapeutic
abortion, or stillbirth (see Figure 10).
- The live birth
per cycle rate shows the percentage of cycles started that
resulted in a live birth (a delivery of one or more living babies).
This rate is the one many people are most interested in when
considering ART because it represents the average chances of having
a live-born infant by using ART. In the graphs and charts in this
report, live birth rate means live birth per cycle rate unless
- The live birth
per egg retrieval rate is the percentage of cycles in which eggs
were retrieved that resulted in a live birth. It is generally higher
than the live birth per cycle rate because it excludes those cycles
that were canceled before egg retrieval was carried out. In 1997,
approximately 14% of all fresh, nondonor cycles were canceled.
Cycles are canceled for many reasons: eggs may not develop, the
patient may become ill, or the patient may choose to stop treatment.
- The live birth
per transfer rate includes only those cycles in which an embryo
or egg and sperm were transferred back to the woman. It excludes
cycles in which the egg was not fertilized or the embryos formed
were abnormal and thus no transfer could occur. This rate is
generally the highest of the four measures of ART success.
are the live birth rates for different types of ART procedures?
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 womans
abdomen to transfer the embryos or gametes into the fallopian tubes. In
contrast, IVF involves transferring embryos into a womans uterus
through the cervix without surgery.
Figures 9 through 17
present results of all ART (IVF, GIFT, and ZIFT) procedures from fresh,
non-donor cycles together because the numbers of ZIFT and GIFT
procedures are relatively small.
percentage of ART cycles results in a pregnancy?
Most ART cycles
performed in 1997 (70.5%) did not produce a pregnancy. Figure 9 shows
the results of the 1997 fresh, nondonor cycles. Of all ART cycles, 29.5%
resulted in a pregnancy. More specifically,
- 14.8% produced a
single live birth.
- 9.2% resulted in a
- 5.0% had an
adverse outcome (ectopic pregnancy, miscarriage, induced abortion,
Although a multiple
birth is counted as one live birth, multiple births are presented here
as a separate category because they are often associated with adverse
outcomes or other problems. Newborn deaths and birth defects are not
included as adverse outcomes because the available information for these
outcomes is incomplete. Information on multifetal pregnancy reductions
is also incomplete and thus not provided.
*A multiple birth is
counted as one live birth because it is a single delivery. The total
live birth rate (single and multiple) was 24%.
percentage of pregnancies results in a live birth or multiple birth?
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.
success rates differ among women of different ages?
womans 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.
does a womans age affect her chances of success at the various stages
12 shows that a womans chances of success using ART (with her own
eggs) decrease at every stage of ART as her age increases.
- As women get
older, the likelihood of a successful response to ovarian
stimulation and progression to egg retrieval decreases.
- As women get
older, cycles that have progressed to egg retrieval are slightly
less likely to reach transfer. Thus, as women get older, the
overall likelihood of cycles progressing from start to transfer
- The percentage of
cycles that progress from transfer to pregnancy also
decreases as women get older. This decrease contributes to the
overall decrease in the likelihood of a cycle progressing from start
to pregnancy as women get older.
- As women get
older, cycles that have progressed to pregnancy are less likely to
result in a live birth. Cumulatively, live births occurred in
31% of cycles started in 1997 among women younger than 35, 26% among
women aged 35-37, 17% among women aged 38-40, and 8% among women
older than 40.
In 1997, a total of
55,002 fresh, nondonor cycles were started:
- 24,581 among women
- 12,733 among women
- 10,997 among women
- 6,691 among women
the chances of success using ART compare for women who have previously
given birth and women
who have not?
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.
the cause of infertility affect the chances of success using ART?
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.
ART cycle more likely to be successful when more embryos are
Figure 15 shows the
relationship between the number of embryos transferred during an ART
procedure in 1997 and the number of infants born alive as a result of
that procedure. In general, transferring multiple embryos during an ART
cycle improves the chances for a live birth but also increases the
possibility of a multiple birth. Multiple births are of concern because
of the additional health risks they create for both mothers and infants
(e.g., higher rates of caesarean-section, prematurity, low birth weight,
and infant death and disability).
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
ART cycle more likely to be successful for couples with male factor
infertility when ICSI is used?
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
the size of the clinic affect its success rate?
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
represent the average success rates for clinics in that quartile.
For the exact number of cycles and success rates at an individual
clinic, refer to the clinic table section of this report.
What are the success rates
for ART using frozen embryos?
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.
Are older women more
likely to have ART using donor eggs?
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 womans 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.
What are the
success rates for ART
when donor eggs are used?
20 compares success rates for ART using donor eggs with those for ART using a
womans 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
womans own eggs declines steadily as women get older.
Fertility Clinic Tables
In this section, each
clinic's data are presented in a one-page table that includes individual program
characteristics, the types of ART used, patient diagnoses, and success rates
that each clinic reported and verified for 1997. Clinics are listed in
alphabetical order by state, city, and clinic. The first table in this section
is the national summary of data from all clinics.
considering ART will want to use this report to find the best clinic.
However, 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 different ART treatments that attract particular types of
patients. These and other factors to consider when interpreting clinic data are
Factors to Consider When Using These Tables to
Assess a Clinic
statistics are for 1997. Data
for cycles started in 1997 could not be published until 1999 because the
final outcomes of pregnancies conceived in December 1997 were not known
until October 1998. Additional time was then required to collect and analyze
the data and prepare the report. Many factors that contribute to a clinics
success rate may have changed, for better or for worse, in the 2 years since
these procedures were performed. Personnel may be different. Equipment and
training may or may not have been updated. As a result, success rates for
1997 may differ from current rates.
reported success rate is absolute. A
clinics success rates will vary from year to year even if all determining
factors remain the same. However, the more cycles that a clinic carries out,
the less the rate is likely to vary. Conversely, clinics that carry out
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
clinics success rate in that category would be either 0% or 100%. For
further detail, see the explanation of confidence intervals.
clinics see more than the average number of patients with difficult
infertility problems. Some
clinics are willing to offer ART to most potential users, even those who
have a low probability of success. Others discourage such patients or
encourage them to use donor eggs, a practice that results in higher success
rates among older women. Clinics that accept a higher percentage of women
who have had multiple previous unsuccessful ART cycles will generally have
lower success rates than clinics that do not. In contrast, clinics that
offer ART procedures to patients who might have become pregnant with less
technologically advanced treatment will have higher success rates than
clinics that do not.
A related issue is that success rates shown in this report are presented in
terms of cycles, as required by law, rather than in terms of women. As a
result, women who had more than one ART cycle in 1997 are represented in
multiple cycles. If a woman who received several ART cycles at a given
clinic either never had a successful cycle or had a successful cycle only
after numerous attempts, the clinics success rates would be lowered.
rates affect a clinics success rate. Some
clinics are more likely than others to cancel a cycle if a woman produces
only a small number of eggs. Cancellation rates for fresh, nondonor cycles
vary among clinics from less than 1% to approximately 30%. A high
cancellation rate tends to lower the live birth per cycle rate but may
increase the live birth per retrieval and live birth per transfer rates.
rates for unstimulated (or "natural") cycles are included with
those for stimulated cycles. In
an unstimulated cycle, the woman ovulates naturally rather than through the
daily injections required by stimulated cycles. Unstimulated cycles are less
expensive because they require no daily injections and fewer ultrasounds and
blood tests. However, women who use natural or mild stimulation produce only
one or two follicles, thus reducing the potential number of embryos for
transfer. As a result, unstimulated cycles have lower success rates, and
clinics that carry out a relatively high proportion of unstimulated cycles
will have lower success rates than those that do not. Nationally, fewer than
1% of ART cycles in 1997 were unstimulated. However, in a very few clinics,
more than 25% of cycles were unstimulated.
rates for GIFT and ZIFT are reported together with those for IVF.
Because success rates for
GIFT may be higher than rates for IVF, clinics that do more GIFT procedures
will have higher success rates. However, many women are not suitable
candidates for GIFT or ZIFT. As previously mentioned in this report,
GIFT and ZIFT are more invasive than IVF, and many clinics perform very few
GIFT and ZIFT procedures.
births resulting from extra embryos from a stimulated cycle that were frozen
and transferred at a later date are counted only under frozen cycles.
Clinics that have very good
live birth rates with frozen embryos would have higher ART success rates if
live births from frozen embryos were included as a success for the original
stimulated cycle. Consumers should look at rates for both fresh and frozen
cycles when assessing a clinics success rates.
number of embryos transferred varies from clinic to clinic. In
1997, the average number of embryos that a clinic transferred to women
younger than age 35 ranged from 1.0 to 6.2 for fresh nondonor cycles. The
American Society for Reproductive Medicine and the Society for Assisted
Reproductive Technology discourage the transfer of a large number of embryos
because it increases the likelihood of multiple gestations. Multiple
gestations, in turn, increase both the probability of premature birth and
its related problems and the need for multifetal pregnancy reductions.
success rates can be affected by many other factors, including
of sperm (including motility and ability to penetrate the egg).
and competence of the treatment team.
health of the woman.
consumers considering ART to contact clinics to discuss their specific medical
situation and their potential for success using ART. Because clinics did not
have the opportunity to provide a narrative to explain their data, such a
conversation could provide additional information to help people decide whether
or not to use ART.
offers important options for the treatment of infertility, the decision to use
ART involves many factors in addition to success rates. Going through repeated
ART cycles requires substantial commitments of time, effort, money, and
emotional energy. Therefore, consumers should carefully examine all related
financial, psychological, and medical issues before beginning treatment. They
will also want to consider the location of the clinic, the counseling and
support services available, and the rapport that staff have with their
of how to read a fertility clinic table begins in the next section.
How to Read a
Fertility Clinic Table
This section is
provided to help consumers understand the information presented in the
fertility clinic tables. The number before each heading refers to the
number of the corresponding section in the sample clinic table on the
opposite page. Technical terms are defined in the glossary.
of the 335 clinics reporting data from 1997 are SART members.
women and gestational carriersClinics
have varying policies regarding ART services for single (unmarried)
women and gestational carriers (women who carry a child for another
woman; sometimes referred to as gestational surrogates).
Some clinics have programs for ART using donor eggs.
of donor eggs
Sharing of donor eggs refers to donor cycles in which eggs from a
single donor are given to more than one woman. Policies regarding
sharing of donor eggs vary from clinic to clinic.
Type of ART Used
fertility clinic tables, ART success rates are not broken down into IVF,
GIFT, and ZIFT. (See glossary for definitions.) Because the percentages
of GIFT and ZIFT are usually small, these three types of ART are
combined. However, knowing the percentage of each type of procedure
performed can be useful because carrying out a higher percentage of GIFT
procedures may increase a clinics success rate. This section also
indicates the percentage of procedures that involved intracytoplasmic
sperm injection (ICSI), which not all clinics performed in 1997, and the
percentage of cycles that were unstimulated.
ART Patient Diagnosis
Consumers may want to know what percentage of a particular clinics
patients have the same diagnosis as they do. (See the glossary for
definitions of diagnoses.) In addition, patients diagnoses may affect
a clinics success rates. However, the use of these diagnostic
categories may vary from clinic to clinic, and the definitions are
imprecise. Thus, these statistics should be applied with caution.
Success Rates by Type of Cycle
Success rates are given for the three types 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
success rates indicate the average chance of success for the given
procedure at the clinic in 1997 for each of four age groups. Success
rates are calculated as either the number of pregnancies or the number
of live births from ART for every hundred cycles started, egg
retrievals, or embryo transfers at the clinic in 1997. For example, if a
clinic started a total of 50 cycles in 1997, and 15 live births
resulted, the average success rate for cycles started at that clinic per
100 cycles would be
the success rate for live births per 100 cycles is 30.
fewer than 20 cycles are reported in a given category, the rates are
shown as fractions rather than in terms of 100 cycles. For example, the
sample clinic carried out only four frozen cycles using donor eggs among
women younger than age 35. Of these four cycles, twoor 50 per 100
cycleswere successful. However, because of the small number of
cycles, 50 live births per 100 cycles is not a reliable success rate, so
the success rate is presented as 2/4.
cycles were performed in a category, no rates or embryo transfer
averages could be calculated, so these spaces are blank. (For an
example, see frozen embryo cycles among women aged 3840 and older
than 40 in the sample clinic table.)
Cycles Using Fresh Embryos From Nondonor Eggs
This section includes IVF, GIFT, and ZIFT cycles that used a womans
own eggs. Cycles that used frozen embryos or donor eggs are not included
per 100 cycles
(Number of pregnancies divided by number of cycles started,
expressed in terms of 100 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.
births per 100 cycles
(Number of live births divided by number of cycles started,
expressed in terms of 100 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 (i.e., a multiple birth is counted as one live
births per 100 retrievals
of live births divided by number of egg retrievals, expressed in
terms of 100 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 is often 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 birth per cycle started rate.
births per 100 transfers
(Number of live births divided by number of embryo transfers,
expressed in terms of 100 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
womans uterus, or in the case of GIFT and ZIFT, egg and sperm or
embryos were transferred into the womans 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 will
be higher than those reported for egg retrievals and for cycles
per 100 cycles
(Number of cycles canceled divided by the total number of cycles,
expressed in terms of 100 cycles)
This number refers to the cycles that were stopped before an egg was
retrieved. A cycle may be canceled if a womans ovaries do not
respond to fertility medications and thus produce an insufficient
number of follicles. Cycles are also canceled because of illness or
other medical or personal reasons.
number of embryos transferred
number of embryos per embryo transfer procedure)
The average number of embryos transferred varies from clinic to
clinic. The American Society for Reproductive Medicine and the
Society for Assisted Reproductive Technology have practice
guidelines that address this issue.
gestations per 100 pregnancies
of pregnancies with two fetuses divided by the total number of
pregnancies, expressed in terms of 100 pregnancies)
A gestation with two or more fetuses is counted as one pregnancy.
or greater gestations per 100 pregnancies
of pregnancies with three or more fetuses divided by the total
number of pregnancies, expressed in terms of 100 pregnancies)
Multiple gestations can be associated with increased risk for
mothers and babies (e.g., higher caesarean-section rates,
prematurity, and low birth weight) and the possibility for
A gestation with two or more fetuses is counted as one pregnancy.
live births per 100 live births
of deliveries resulting in the birth of more than one living baby
divided by the total number of live births, expressed in terms of
100 live births)
A delivery of one or more living babies is counted as one live
Cycles Using Frozen Embryos From Nondonor Eggs
Frozen (cryopreserved) cycles are those in which previously frozen
embryos are thawed and then transferred. Because frozen cycles use
embryos formed from a previous stimulated cycle, no stimulation or
retrieval is involved. As a result, these cycles are usually less
expensive and less invasive than cycles using fresh embryos. In
addition, freezing some of the embryos from a retrieval procedure may
increase a womans overall chances of having a child from a single
Cycles Using Donor Eggs
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 and healthy woman. Embryos donated by couples who previously had
ART may also be available. Many clinics provide services for donor egg
and embryo cycles. Live birth rates do not vary much by the recipients
age when donor eggs or embryos are used. (See Figure 20.)
Age of Woman
Because a womans fertility declines with age, clinics report lower
success rates for older women attempting to become pregnant with their
own eggs. For this reason, rates are reported separately for women
younger than age 35, for women aged 3537 years, for women aged 38
40 years, and for women older than age 40. The sample clinic profile
illustrates the decline in ART success rates among older women: 100
cycles started at this clinic in women younger than age 35 resulted in
24.6 live births, whereas 100 cycles in women older than age 40 resulted
in only 6.9 live births.
95% Confidence Interval
The tables show 95% confidence intervals for live births per 100 cycles
unless fewer than 20 cycles are reported in an age category. The 95%
confidence interval tells us how reliable a clinics success rate is.
In general, the more cycles that a clinic performs, the narrower the
range of its confidence interval and the more likely the clinic would be
to have the same success rate if it treated other similar groups of
patients under similar clinical conditions.
though one clinic's success rate may appear higher than anothers
based on the confidence intervals, confidence intervals are only
one indication that the success rate may be better. Other factors must
also be considered when comparing rates from two clinics. For
example, some clinics see more than the average number of patients with
difficult infertility problems, while others discourage patients with a
low probability of success. Click here for further information on
important factors to consider when using the tables to assess a clinic.
here for a more detailed explanation and examples of confidence
intervals (included in the Appendix).
to Interpret a Confidence Interval
What is a
confidence intervals are a useful way to consider margin of error, a statistic
often used in voter polls to indicate the range within which a value is likely
to be correct (e.g., 30% of the voters favor a particular candidate with a
margin of error of + 3.5%). Similarly, in this report, confidence intervals are
used to provide a range that we can be quite confident contains the success rate
for a particular clinic during a particular time.
Why do we
need to consider confidence intervals if we already know the exact success rates
for each clinic in 1997?
No success rate
or statistic is absolute. Suppose a clinic performed 100 cycles among women
younger than 35 in 1997 and had a success rate of 20% with a confidence interval
of 12%-28%. The 20% success rate tells us that the average chance of success for
women younger than 35 treated at this clinic in 1997 was 20%. How likely is it
that the clinic could repeat this performance? For example, if the same clinic
performed another 100 cycles under similar clinical conditions on women with
similar characteristics, would the success rate again be 20%? The confidence
interval tells us that the success rate would be likely to fall between 12% and
the size of the confidence interval vary for different clinics?
The size of the
confidence interval gives us a realistic sense of how secure we feel about the
success rate. If the clinic had performed only 20 cycles among women younger
than 35 instead of 100 and still had a 20% success rate (4 successes out of 20
cycles), the confidence interval would be much larger (between 3% and 37%)
because the success or failure of each individual cycle would count for more.
For example, if just one more cycle had resulted in a live birth, the success
rate would have been substantially higher25%, or 5 successes out of 20
cycles. Likewise, if just one more cycle had not been successful, the success
rate would have been substantially lower15%, or 3 out of 20 cycles. Compare
this scenario to the original example of the clinic that performed 100 cycles
and had a 20% success rate. If just one more cycle had resulted in a live birth,
the success rate would only have changed slightly, from 20% to 21%, and if one
more cycle had not been successful, the success rate would only have fallen to
19%. Thus, our confidence in a 20% success rate depends on how many cycles were
confidence intervals be considered when success rates from different clinics are
intervals should be considered because success rates can be misleading. For
example, if Clinic A performs 20 cycles in a year and 8 cycles result in a live
birth, its live birth rate would be 40%. If Clinic B performs 600 cycles and 180
result in a live birth, its live birth rate would be 30%. We might be tempted to
say that Clinic A has a better success rate than Clinic B. However, because
Clinic A performed few cycles, its success rate would have a wide 95% confidence
interval of 18.5%-61.5%. On the other hand, because Clinic B performed a large
number of cycles, its success rate would have a relatively narrow confidence
interval of 26.2%33.8%. Thus, Clinic A could have a rate as low as 18.5% and
Clinic B could have a rate as high as 33.8% if each clinic repeated its
treatment with similar patients under similar clinical conditions. Moreover,
Clinic Bs rate is much more likely to be reliable because the size of its
confidence interval is much smaller than Clinic As.
of ART a
|Sharing of donor eggs?
comparison of clinic success rates may not be meaningful because
patient medical characteristics and treatment approaches vary from
clinic to clinic.
ART Pregnancy Success Rates
Embryos From Nondonor Eggs
|Number of cycles
|Pregnancies per 100
births per 100 cyclesc
|Live births per 100
|Live births per 100
|Cancellations per 100
per 100 pregnancies
|Triplet or more gestations per 100
birth per 100 live birthsc
Embryos From Nondonor Eggs
|Number of transfers
|Live births per 100 transfers c
|Average number embryos transferred
|Number of fresh transfers
|Live births per 100 fresh transfers c
|Number of frozen transfers
|Live births per 100 frozen transfers
|Average number embryos transferred
(fresh and frozen)
Includes only fresh nondonor egg cycles.
b Combination of fresh, nondonor IVF, GIFT, and
c A multiple birth is counted as one live birth.
Fertility Clinic Reports by State
of Terms Used in This Report
A pregnancy that does
not result in a live birth. The adverse outcomes reported for ART
procedures are miscarriages, ectopic (tubal) pregnancies, induced
abortions, and stillbirths.
for Reproductive Medicine (ASRM)
A professional society
whose affiliate organization, the Society for Assisted Reproductive
Technology (SART), reports annual fertility clinic data to the Centers
for Disease Control and Prevention (CDC).
All treatments or
procedures that involve surgically removing eggs from a womans
ovaries and combining the eggs with sperm to help a woman become
pregnant. The types of ART are in vitro fertilization, gamete
intrafallopian transfer, and zygote intrafallopian transfer.
A process in which 1)
an ART procedure is carried out, 2) a woman has undergone ovarian
stimulation or monitoring with the intent of having an ART procedure, or
3) frozen embryos have been thawed with the intent of transferring them
to a woman. A cycle begins when a woman begins taking fertility drugs or
having her ovaries monitored for follicle production.
An ART cycle in which ovarian
stimulation was carried out but which was stopped before eggs were
retrieved, or in the case of frozen embryo cycles, before embryos were
Disease Control and Prevention (CDC)
A government agency within the
U.S. Department of Health and Human Services responsible for publishing
annual fertility clinic success rates.
An embryo formed from the egg of
one woman (the donor) and then transferred to another woman who is
unable to conceive with her own eggs (the recipient). The donor
relinquishes all parental rights to any resulting offspring.
A pregnancy in which the
fertilized egg implants in a location outside of the uterus usually
in the fallopian tube, the ovary, or the abdominal cavity. Ectopic
pregnancy is a dangerous condition that must receive prompt
A female reproductive cell, also
called an oocyte or ovum.
retrieval (also called oocyte retrieval)
A procedure to collect the eggs
contained in the ovarian follicles.
(also called oocyte transfer)
The transfer of retrieved eggs
into a woman's fallopian tubes through laparoscopy (see definition).
This procedure is used only in GIFT (see definition).
An egg that has been fertilized
by a sperm and undergone one or more divisions.
Placement of embryos into a woman's uterus through the cervix after in
vitro fertilization; in zygote intrafallopian transfer (ZIFT) (see
definition), the embryos are placed in a womans fallopian tube.
A medical condition involving the presence of tissue similar to the
uterine lining in locations outside of the uterus, such as the ovaries,
fallopian tubes, and abdominal cavity.
The penetration of the egg by the sperm and the resulting combining of
genetic material that develops into an embryo.
The unborn offspring from the eighth week after conception to the moment
A structure in the ovaries that contains a developing egg.
Fresh eggs, sperm,
Eggs, sperm, or embryos that have not been frozen. However, fresh
embryos may have been conceived using fresh or frozen sperm.
A cycle in which embryos are preserved through freezing (cryopreservation)
for transfer at a later date.
A reproductive cell, either a sperm or egg.
An ART procedure that involves removing eggs from the womans ovary,
combining them with sperm, and using a laparoscope to place the
unfertilized eggs and sperm into the woman's fallopian tube through
small incisions in her abdomen.
The period of time from conception to birth
carrier (also called a gestational surrogate)
A woman who carries an embryo that was formed from the egg of another
woman. The gestational carrier usually has a contractual obligation to
return the infant to its intended parents.
A fluid-filled structure that develops within the uterus early in
pregnancy. In a normal pregnancy, a gestational sac contains a
A procedure in which a single sperm is injected directly into an egg;
this procedure is most commonly used to overcome male infertility
A surgical or other medical procedure used to end a pregnancy.
A medical procedure that involves placing sperm into a womans uterus
to facilitate fertilization. IUI is not considered an ART procedure
because it does not involve the manipulation of eggs.
IVF (in vitro
An ART procedure that involves removing eggs from a womans ovaries
and fertilizing them outside her body. The resulting embryos are then
transferred into the womans uterus through the cervix.
A surgical procedure in which a fiber optic instrument (a laparoscope)
is inserted through a small incision in the abdomen to view the inside
of the pelvis.
The delivery of one or more babies with any signs of life.
Any cause of infertility due to deficiencies in sperm quantity or that
make it difficult for a sperm to fertilize an egg under normal
called spontaneous abortion)
A pregnancy ending in the spontaneous loss of the embryo or fetus before
20 weeks of gestation.
A procedure used to decrease the number of fetuses a woman carries and
improve the chances that the remaining fetuses will develop into healthy
infants. Multifetal reductions that occur naturally are referred to as
spontaneous multifetal reductions.
A pregnancy that results in the birth of more than one infant.
A pregnancy with multiple fetuses.
The female reproductive cell, also called an egg.
The use of ultrasound and/or blood or urine tests to monitor follicle
development and hormone production.
The use of drugs to stimulate the ovaries to develop follicles and
A cause of infertility due to problems with egg production by the
Pregnancy documented by the presence of a gestational sac on ultrasound.
For ART data collection purposes, pregnancy is defined as a clinical
pregnancy rather than a chemical pregnancy (i.e., a positive pregnancy
A national, nonprofit consumer organization offering education,
advocacy, and support to those experiencing infertility. Services
include a national HelpLine, quarterly newsletter, extensive literature
list, member-to-member contact systems, and local support groups through
a network of over 50 chapters nationwide.
for Assisted Reproductive Technology (SART)
An affiliate of the
American Society for Reproductive Medicine composed of clinics and
programs that provide ART. SART reports annual fertility clinic data to
The male reproductive cell.
An infant delivered without signs of life after 20 or more weeks of
An ART cycle in which a woman receives oral or injected fertility drugs
to stimulate her ovaries to produce more follicles.
A cycle in which frozen embryos are thawed for transfer.
Structural or functional damage to one or both fallopian tubes that
A technique used in ART for visualizing the follicles in the ovaries and
the gestational sac or fetus in the uterus.
Infertility for which no cause has been determined despite a
An ART cycle in which the woman does not receive drugs to stimulate her
ovaries to produce more follicles. Instead, follicles develop
A disorder in the uterus (e.g., fibroid tumors) that reduces
(zygote intrafallopian transfer)
An ART procedure in which eggs are collected from a woman's ovary and
fertilized outside her body. A laparoscope is then used to place the
resulting zygote (fertilized egg) into the womans fallopian tube
through a small incision in her abdomen.
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