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2005 Assisted Reproductive Technology (ART) Report: Section 2—ART
Cycles Using Fresh, Nondonor Eggs or Embryos |
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This
page contains figures 5–15
Section 2A | Section 2B | Section 2C
What are the steps for an ART
cycle using fresh nondonor eggs or embryos?
Figure 5 presents the steps for an ART cycle using fresh nondonor
eggs or embryos and shows how ART users in 2005 progressed through
these stages toward pregnancy and live birth.
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.
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), but sometimes into the fallopian tubes (e.g.,
GIFT, ZIFT).
If one or more of the transferred embryos implant within the
woman’s uterus, the cycle then may progress to clinical pregnancy.
Finally, the pregnancy may progress to a live birth, the delivery
of one or more live-born infants. (The birth of twins, triplets, or
more is counted as one live birth.)
A cycle may be discontinued at any step for specific medical
reasons (e.g., no eggs are produced, the embryo transfer was not
successful) or by patient choice.
Figure
5: Outcome of ART Cycles Using Fresh Nondonor Eggs or Embryos,
by Stage, 2005.
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Why are some ART cycles
discontinued?
In 2005, 11,729 ART cycles (about
12%) were discontinued before the egg retrieval step (see
Figure 5).
Figure 6 shows reasons that the cycles were stopped. For
approximately 83% of these cycles, there was no or inadequate egg
production. Other reasons included too high a response to ovarian
stimulation medications (i.e., potential for ovarian hyperstimulation
syndrome), concurrent medical illness, or a patient’s personal reasons.
Figure 6:
Reasons ART Cycles Using Fresh Nondonor Eggs or Embryos Were
Discontinued in 2005.
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How is the success of ART measured?
Figure 7 shows ART success
rates using six different measures, each providing slightly different
information about this complex process. The vast majority of success
rates have increased slightly each year since CDC began monitoring them
in 1995 (see Section 5).
- Percentage of ART cycles started that produced a pregnancy:
This is higher than the percentage of cycles that resulted in a
live birth because some pregnancies end in miscarriage, induced
abortion, or stillbirth (see Figure 9).
- Percentage of ART cycles started that resulted in a live
birth (a delivery of one or more live-born infants): This is the
one many people are most interested in because it represents the
average chance of having a live-born infant by using ART. This is
referred to as the basic live birth rate in the Fertility Clinic
Success Rate and Certification Act of 1992.
- Percentage of ART cycles in which eggs were retrieved that
resulted in a live birth: This is generally higher than the
percentage of cycles that resulted in a live birth because it
excludes cycles that were canceled before eggs were retrieved. In
2005, about 12% of all cycles using fresh nondonor eggs or embryos
were canceled for a variety of reasons (see
Figure 6). This is referred
to as the live birth rate per successful oocyte (egg) retrieval in
the Fertility Clinic Success Rate and Certification Act of 1992.
- Percentage of ART cycles in which an embryo or egg and sperm
transfer occurred that resulted in a live birth: This is the
highest of these six measures of ART success.
- Percentage of ART cycles started that resulted in a singleton
live birth: Overall, singleton live 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 ART cycles in which an embryo or egg and sperm
transfer occurred that resulted in a singleton live birth: This
is higher than the percentage of ART cycles started that resulted in
a singleton live birth because not all ART cycles proceed to embryo
transfer.
Figure
7: Success Rates for ART Cycles Using Fresh Nondonor Eggs or Embryos,
by Different Measures, 2005.
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What percentage of ART cycles results in a
pregnancy?
Figure 8 shows the
results of ART cycles in 2005 that used fresh nondonor eggs or embryos.
Most of these cycles (65%) did not produce a pregnancy; a very small
proportion (0.6%) resulted in an ectopic pregnancy (the embryo implanted
outside the uterus), and 34% resulted in clinical pregnancy. Clinical
pregnancies can be further subdivided as follows:
- 20.5% resulted in a single-fetus pregnancy.
- 11.2% resulted in a multiple-fetus pregnancy.
- 2.3% ended in miscarriage before the number of fetuses could be
accurately determined.
Figure 8:
Results of ART Cycles Using Fresh Nondonor Eggs or Embryos, 2005. |
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What percentage of
pregnancies results in a live birth?
Figure 9 shows the outcomes
of pregnancies resulting from ART cycles in 2005 (see
Figure 8).
Approximately 82% of the pregnancies resulted in a live birth (56% in a
singleton birth and 26% in a multiple-infant birth). About 18% of
pregnancies resulted in an adverse outcome (miscarriage, induced
abortion, or stillbirth). For 0.7% of pregnancies, the outcome was
unknown.Although the birth of more than one infant is counted as one
live birth, multiple-infant births are presented here as a separate
category because they often are associated with problems for both
mothers and infants. Infant deaths and birth defects are not included as
adverse outcomes because the available information for these outcomes is
incomplete.
Figure
9: Outcomes of Pregnancies Resulting from ART Cycles Using Fresh
Nondonor Eggs or Embryos, 2005. |
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Using ART, what is the risk of having a multiple-fetus
pregnancy or multiple-infant live birth?
Multiple-infant births are associated with greater problems for both
mothers and infants, including higher rates of caesarean section,
prematurity, low birth weight, and infant disability or death.
Part A of Figure 10 shows
that among the 33,101 pregnancies that resulted from ART cycles using
fresh nondonor eggs or embryos, 60% were singleton pregnancies, 28% were
twins, and about 4% were triplets or more. Seven percent of pregnancies
ended in miscarriage in which the number of fetuses could not be
accurately determined. Therefore, the percentage of pregnancies with
more than one fetus might have been higher than what was reported (about
33%).
In 2005, 5,812 pregnancies resulting from ART cycles ended in either
miscarriage, stillbirth, or induced abortion, and 239 pregnancy outcomes
were not reported. The remaining 27,047 pregnancies resulted in live
births. Part B of Figure 10
shows that approximately 32% of these live births produced more than one
infant (30% twins and approximately 2% triplets or more). This compares
with a multiple-infant birth rate of slightly more than 3% in the
general U.S. population.
Although the total rates for multiples were similar between pregnancies
and live births, there were more triplet-or-more pregnancies than
births. Triplet-or-more pregnancies may be reduced to twins or
singletons by the time of birth. This can happen naturally (e.g., fetal
death), or a woman and her doctor may decide to reduce the number of
fetuses using a procedure called multifetal pregnancy reduction. CDC
does not collect information on multifetal pregnancy reductions.
Figure 10: Risks of
Having Multiple-Fetus Pregnancy and Multiple-Infant Live Birth from ART
Cycles Using Fresh Nondonor Eggs or Embryos, 2005. |
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Using ART, what is the risk for preterm birth?
Preterm birth occurs when a woman gives birth before 37 full
weeks of pregnancy. Infants born preterm are at greater risk for
death in the first few days of life, as well as other adverse
health outcomes including mental retardation, visual and hearing
impairments, learning disabilities, and behavioral and emotional
problems throughout life. Preterm births also cause substantial
emotional and economic burdens for families.
Figure 11 shows
percentages of preterm births resulting from ART cycles that
used fresh nondonor eggs or embryos, by the number of infants
born. For singletons, it shows separately the preterm rate for
pregnancies that started with one fetus (single-fetus
pregnancies) or more than one (multiple-fetus pregnancies).
Among singletons, the percentage of preterm births was higher
for those from multiple-fetus pregnancies (22%) than those from
single-fetus pregnancies (13%). In the general U.S. population,
where singletons are almost always the result of a single-fetus
pregnancy, 11% were born preterm in 2004 (most recent available
data).
Among ART births, 62% of twins and 97% of triplets or more
were born preterm. A comparison of preterm births between ART
twins and triplets or more and similar births in the general
population is not meaningful because the vast majority of
multiple-infant births in the United States are due to
infertility treatments (both ART and non-ART).
These data indicate that the risk for preterm birth is higher
among infants conceived through ART than for infants in the
general population. This increase in risk is, in large part, due
to the higher rate of multiple-infant pregnancies resulting from
ART cycles.
Figure 11: Percentages of
Preterm Births from ART Cycles Using Fresh Nondonor Eggs or Embryos, by
Number of Infants Born, 2005. |
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Using ART, what is the risk of having low-birth–weight
infants?
Low-birth–weight infants (less than 2,500 grams, or 5
pounds, 9 ounces) are at increased risk for death and short- and
long-term disabilities such as cerebral palsy, mental retardation, and
limitations in motor and cognitive skills.
Figure 12 presents
percentages of low-birth–weight infants resulting from ART cycles that
used fresh nondonor eggs or embryos, by number of infants born. For
singletons, it shows separately the rates of low birth weight among
infants born from pregnancies that started with one fetus (single-fetus
pregnancies) and with more than one fetus (multiple-fetus pregnancies).
Among singletons born through ART, the percentage of
low-birth–weight infants was higher for those from multiple-fetus
pregnancies (17%) than those from single-fetus pregnancies (9%). In the
general U.S. population, where singletons are almost always the result
of a single-fetus pregnancy, 6% of infants born in 2004 (most recent
available data) had low birth weights.
Approximately 56% of twins and 92% of triplets or more
had low birth weights. Comparing rates of low birth weight between ART
twins and triplets or more and the general population is not meaningful
because the vast majority of multiple births in the United States are
due to infertility treatments (both ART and non-ART).
These data indicate that the risk for low birth weight
is higher for infants conceived through ART than for infants in the
general population. The increase in risk is due, in large part, to the
higher rate of multiple-infant pregnancies resulting from ART cycles.
Figure 12: Percentages
of Low Birth Weight Infants from ART Cycles Using Fresh Nondonor Eggs or
Embryos, by Number of Infants Born, 2005. |
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What are the ages of women who use ART?
Figure 13 presents ART cycles
using fresh nondonor eggs or embryos according to the age of the woman
who had the procedure. About 12% of these cycles were among women
younger than age 30, 68% were among women aged 30–39, and approximately
21% were among women aged 40 and older.
Figure 13:
Age Distribution of Women Who Had ART Cycles Using Fresh Nondonor Eggs
or Embryos, 2005.
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Do ART success rates differ among women of different
ages?
A woman’s age is the most important factor affecting the
chances of a live birth when her own eggs are used.
Figure 14 shows the percentages of
pregnancies, live births, and singleton live births for women of
different ages who had ART procedures using fresh nondonor eggs or
embryos in 2005. The percentages of ART cycles resulting in live births
and singleton live births are different because of the high percentage
of multiple-infant deliveries counted among the total live births. The
percentage of multiple-infant births is particularly high among women
younger than 35 (see Figure 34).
Among women in their 20s, the percentages of ART cycles resulting in
pregnancies, live births, and singleton live births were relatively
stable; however, success rates declined steadily from the mid-30s
onward. For additional detail on success rates among women aged 40 or
older, see Figure 15.
Figure 14:
Percentages of ART Cycles Using Fresh Nondonor Eggs or Embryos
That Resulted in Pregnancies, Live Births, and Singleton Live
Births, by Age of Woman, 2005.
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How do ART success rates differ for women who
are 40 or older?
Success rates decline with each year of age and are particularly low for
women 40 or older. Figure 15
shows the percentages of pregnancies, live births, and singleton live
births in 2005 for women 40 or older who used fresh nondonor eggs or
embryos. The average chance for pregnancy was 23% for women age 40; the
percentage of ART cycles resulting in live births for this age was about
16%, and the percentage of ART cycles resulting in singleton live births
was about 13%. All percentages dropped steadily with each 1-year
increase in age. For women older than 44, the percentages of live births
and singleton live births were both a little less than 1%. Women 40 or
older generally have much higher success rates using donor eggs (see
Figure 45).
Figure 15:
Percentages of ART Cycles Using Fresh Nondonor Eggs or Embryos
That Resulted in Pregnancies, Live Births, and Singleton Live
Births Among Women Aged 40 or Older, 2005. |
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Section
1 | Section 2 |
Section
3 | Section 4 |
Section
5
Previous ART Reports
Implementation of the Fertility
Clinic Success Rate and Certification Act of 1992
Assisted Reproductive Technology: Embryo
Laboratory
Page last reviewed: 12/12/07
Page last modified: 12/12/07
Content source: Division
of Reproductive Health,
National Center for Chronic Disease
Prevention and Health Promotion
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