|
2004 Assisted Reproductive Technology (ART) Report: Section 2—ART
Cycles Using Fresh, Nondonor Eggs or Embryos |
|
This
page contains figures 5–15
Section
2A | Section
2B | Section 2C
What are the steps for an ART procedure 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 2004 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, 2004.
|
|
Why are some ART
cycles discontinued?
In 2004, 11,767 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 2004.
|
|
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 rates have
increased slightly each year since CDC began monitoring them in 1995 (see
Section 5).
-
Pregnancy per cycle rate: the percentage of ART
cycles started that produced a pregnancy. This rate is higher than the
live birth per cycle rate because some pregnancies end in miscarriage,
induced abortion, or stillbirth (see
Figure 7).
-
Live birth per cycle rate: the percentage of ART
cycles started that resulted in a live birth (a delivery of one or more
live-born infants). This rate is the one many people are most interested
in because it represents the average chances of having a live-born infant
by using ART. Throughout this report, live birth rate means live birth
per cycle rate unless otherwise specified.
-
Live birth per egg retrieval rate: the percentage
of ART 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 cycles that were canceled before eggs were retrieved. In 2004,
about 12% of all cycles using fresh nondonor eggs or embryos were canceled
for a variety of reasons (see Figure
6).
-
Live birth per transfer rate: includes only those
ART cycles in which an embryo or egg and sperm were transferred back to
the woman. This rate is the highest of these six measures of ART success.
-
Singleton live birth per cycle rate: the 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.
-
Singleton live birth per transfer rate: the
percentage of ART cycles that resulted in a singleton live birth among ART
cycles in which an embryo or egg and sperm were transferred back to the
woman.
Figure
7: Success Rates for ART Cycles Using Fresh Nondonor Eggs or Embryos,
by Different Measures, 2004.
|
|
What percentage
of ART cycles results in a pregnancy?
Figure 8 shows the results
of ART cycles in 2004 that used fresh nondonor eggs or embryos.
Most of these cycles (66%) did not produce a pregnancy; a very small
proportion (0.7%)
resulted in an ectopic pregnancy (the embryo implanted outside the
uterus), and slightly less
than 34% resulted in clinical pregnancy. Clinical pregnancies can be
further subdivided
as follows:
- 20.3% resulted in a single-fetus pregnancy.
- 11.3% resulted in a multiple-fetus pregnancy.
- 2.1% ended in miscarriage before the number of fetuses could be
accurately determined.
Figure 8: Results of ART
Cycles Using Fresh Nondonor Eggs or Embryos, 2004.
|
|
What
percentage of pregnancies results in a live birth?
Figure 9 shows the outcomes of pregnancies resulting from
ART cycles in 2004 (see Figure 8). Approximately 82% of the pregnancies
resulted in a live birth (55% in a singleton birth and 27% in a
multiple-infant birth). Seventeen percent of pregnancies resulted in an
adverse outcome(miscarriage, induced abortion, or stillbirth). For 0.9%
of pregnancies, the outcome was not reported.
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, 2004. |
|
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 31,758 pregnancies that resulted from ART cycles
using fresh nondonor eggs or embryos, 60% were singleton pregnancies,
29% were twins, and about 5% were triplets or more. Six 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 34%).
In 2004, 5,393 pregnancies resulting from ART cycles
ended in either miscarriage, stillbirth, or induced abortion, and 299
pregnancy outcomes were not reported. The remaining 26,059 pregnancies
resulted in live births. Part B of Figure
10 shows that approximately 33% of these live births produced more
than one infant (30% twins and approximately 3% 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. Information on medical multifetal pregnancy reductions is
incomplete and therefore is not provided here.
Figure 10: Risk of Having
Multiple-Fetus Pregnancy and Multiple-Infant Live Birth from ART Cycles
Using Fresh Nondonor Eggs or Embryos, 2004. |
|
What are the ages of women who use ART?
Figure 11 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 20% were among
women aged 40
and older.
Figure 11: Age Distribution of Women
Who Had ART Cycles Using Fresh Nondonor Eggs or Embryos, 2004. |
|
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 12 shows the pregnancy rates,
live birth rates, and singleton live birth rates for women of different
ages who had ART procedures using fresh nondonor eggs or embryos in
2004. Live birth rates and singleton live birth rates are different
because of the high percentage of multiple-birth deliveries counted
among the total live births. The percentage of multiple births is
particularly high among women younger than 35 (see
Figure 31). Among women in their 20s,
pregnancy rates, live birth rates, and singleton live birth rates were
relatively stable; however, success rates declined steadily from the
mid-30s onward as fertility declined with age. For additional detail on
success rates among women aged 40 years or older, see
Figure 13.
Figure 12: Pregnancy Rates, Live
Birth Rates, and Singleton Live Birth Rates for ART Cycles Using Fresh
Nondonor Eggs or Embryos, by Age of Woman, 2004. |
|
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 13 shows pregnancy rates, live
birth rates, and singleton live birth rates for women 40
or older who used fresh nondonor eggs or embryos. The average chance for
pregnancy was
23% for women age 40; the live birth rate for this age was about 16%,
and the singleton live
birth rate was 12%. All rates dropped steadily with each 1-year increase
in age. For women
older than 44, the live birth rates and singleton live birth rates were
both a little less than 1%.
Women 40 or older generally have much higher success rates using donor
eggs (see Figure
41).
Figure 13: Pregnancy
Rates, Live Birth Rates, and Singleton Live Birth Rates for ART Cycles
Using Fresh Nondonor Eggs or Embryos Among Women Aged 40 or Older, 2004.
|
|
How do miscarriage
rates for ART patients vary among women of different ages?
A woman’s age not only affects the chance for
pregnancy when her own eggs are used, but also affects her risk
for miscarriage. Figure 14
shows miscarriage rates for women of different ages who became
pregnant using ART procedures in 2004. Miscarriage rates were
below 12% among women younger than 34. The rates began to
increase among women in their mid- to late 30s and continued to
increase with age, reaching 28% at age 40 and 59% among women
older than 43.
The miscarriage rates observed among women
undergoing ART procedures using fresh nondonor eggs or embryos
appear to be similar to those reported in various studies of
other pregnant women in the United States.
Figure 14:
Miscarriage Rates Among Women Who Had ART Cycles Using Fresh
Nondonor Eggs or Embryos, by Age of Woman, 2004.
|
|
How does
a woman’s age affect her chances of progressing through the various stages of
ART?
In 2004, a total of 94,242 cycles using fresh nondonor eggs
or embryos were started:
- 40,853 in women younger than 35
- 21,019 in women 35–37
- 19,174 in women 38–40
- 8,487 in women 41–42
- 4,709 in women older than 42
Figure 15 shows that a
woman’s chance of progressing from the beginning of ART to
pregnancy and live birth (using her own eggs) decreases 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.
- The percentage of cycles that progress from transfer to
pregnancy also decreases as
women get older.
- As women get older, cycles that have progressed to
pregnancy are less likely to result in a live birth
because the risk for miscarriage is greater (see
Figure 14).
Overall, 37% of cycles started in 2004 among women younger
than 35 resulted in live births.
This percentage decreased to 29% among women 35–37 years of age,
20% among women
38–40, 11% among women 41–42, and 4% among women older than 42.
As noted in Figures
12 and 13, the proportion
of cycles that resulted in singleton live births is even lower
for each
age group.
Figure 15: Outcomes of ART
Cycles Using Fresh Nondonor Eggs or Embryos, by Stage and Age
Group, 2004. |
|
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
Date last reviewed:
01/14/2007
Content source: Division
of Reproductive Health,
National Center for Chronic Disease
Prevention and Health Promotion
|
|
|