This report marks the eleventh consecutive year that CDC has
published an annual report detailing the success rates for ART
clinics in the United States. Having several years of data provides
us with the opportunity to examine trends in ART use and success
rates over time. Because the first year of data collection, 1995,
did not include non—SART member clinics, we limit our examination of
trends to the years 1996–2005.
Is the use of ART increasing?
Figure 49 shows the numbers of ART
cycles performed, live-birth deliveries, and infants born using ART from 1996 through 2005. The number of ART cycles performed in the United
States has more than doubled, from 64,681 cycles in 1996 to 134,260 in
2005. The number of live-birth deliveries in 2005 (38,910) was more
than two and a half times higher than in 1996 (14,507). The number of
infants born who were conceived using ART also increased steadily
between 1996 and 2005. In 2005, 52,041 infants were born, which
was more than double the 20,840 born in 1996. Because in some cases more
than one infant is born during a live-birth delivery (e.g.,
twins), the total number of infants born is greater than the number of
live-birth deliveries.
Figure 49: Numbers of ART Cycles
Performed, Live-Birth Deliveries, and Infants Born Using ART, 1996–2005.
Have there been improvements in
the percentage of transfers that result in live births?
Figure 50
presents the percentages of transfers that resulted in live births
for the four primary types of ART cycles. Percentages of transfers
that resulted in live births are presented rather than percentages
of cycles that resulted in live births because that is the only way
to directly compare cycles using fresh embryos with those using
frozen embryos.
From 1996 through 2005, the percentage of transfers
resulting in live births for fresh–nondonor cycles increased 22%,
from 28% in 1996 to 34% in 2005. Over the same time period, the
percentage of transfers resulting in live births increased 68% for
frozen–nondonor cycles, 34% for fresh–donor cycles, and 49% for
frozen–donor cycles.
Figure 50: Percentages of Transfers
That Resulted in Live Births, by Type of ART Cycle, 1996–2005.
Have there been improvements in the percentage of
transfers that result in singleton live births?
Singleton live births are an important measure of success because
they have a much lower risk than multiple-infant births for adverse
infant health outcomes, including prematurity, low birth weight,
disability, and death. Figure 51
presents percentages of transfers that resulted in singleton live
births for the four primary types of ART cycles. Percentages of
transfers that resulted in singleton live births are presented
rather than percentages of cycles that resulted in singleton live
births because that is the only way to directly compare cycles using
fresh embryos with those using frozen embryos.
From 1996 through 2005, the percentage of transfers that resulted
in singleton live births for fresh–nondonor cycles increased 35%,
from 17% in 1996 to 23% in 2005. Over the same time period, the
percentage of transfers resulting in singleton live births increased
79% for frozen–nondonor cycles, 36% for fresh–donor cycles, and 48%
for frozen–donor cycles.
Figure 51: Percentages of Transfers That Resulted in Singleton
Live Births, by Type of ART Cycle,
1996–2005.
Have there been improvements in the percentage of
transfers that result in live births for all ART patients or only for
those in particular age groups?
Figure 52
presents percentages of transfers that resulted in live births, by
woman’s age, for ART cycles using fresh nondonor eggs or embryos.
From 1996 through 2005, the percentage of transfers
that resulted in live births for women younger than 35 increased
29%, from 34% in 1996 to 43% in 2005. Over the same time period, the
percentage of transfers that resulted in live births increased 24%
for women 35–37, 18% for women 38–40, 30% for women 41–42, and 7%
for women older than 42.
Figure 52: Percentages of Transfers That Resulted in Live Births
for ART Cycles Using Fresh Nondonor Eggs or Embryos, by Womans Age,
1996–2005.
Have there been improvements in the percentage of
transfers that result in singleton live births for all ART patients or
only for those in particular age groups?
Singleton live births are an important measure of
success because they have a much lower risk than multiple-infant
births for adverse infant health outcomes, including prematurity,
low birth weight, disability, and death.
Figure 53 presents percentages
of transfers that resulted in singleton live births, by woman’s age,
for ART cycles using fresh nondonor eggs or embryos.
From 1996 through 2005, the percentage of transfers
that resulted in singleton live births for women younger than 35
increased about 45%, from 19% in 1996 to 28% in 2005. Over the same
time period, the percentage of transfers that resulted in singleton
live births increased 36% for women 35–37, 23% for women 38–40, 34%
for women 41–42, and 11% for women older than 42.
Figure 53: Percentages of Transfers (Using Fresh Nondonor Eggs or Embryos) That Resulted in Singleton Live Births, by
Woman’s Age, 1996–2005.
Has the number of embryos
transferred in fresh–nondonor cycles changed?
Figure 54
presents the trends for number of embryos transferred in fresh–nondonor
cycles that progressed to the embryo transfer stage. From 1996 to
2005, cycles that involved the transfer of one embryo increased
slightly, from 6% to 9%; cycles that involved the transfer of two
embryos increased dramatically, from 10% in 1996 to 43% in 2005.
Cycles that involved the transfer of three embryos increased from
23% in 1996 to 29% in 2005, and cycles that involved the transfer of
four or more embryos decreased from 62% in 1996 to 18% in 2005.
Figure 54:
Percentages of Fresh–Nondonor Cycles That Involved the Transfer of
One, Two, Three, or Four or More Embryos, 1996–2005.
Has the number of embryos transferred in each ART cycle
changed for women younger than 35 who have more embryos available than
they choose to transfer?
As shown in Figure
54, the number of embryos transferred in fresh–nondonor cycles
has decreased during the past 10 years.
Figure 55 shows the change over
time in the number of embryos transferred for ART procedures in
which the woman was younger than 35 and the couple chose to set
aside some embryos for future cycles rather than transfer all
available embryos at one time. Previous research suggests that the
number of embryos available for an ART cycle is important in
predicting success. Younger women also tend to have higher success
rates (see Figure 14).
Overall, the number of embryos transferred decreased
among couples who chose to transfer fewer embryos than were
available. In 1996, almost two-thirds (64%) of ART cycles involved
the transfer of four or more embryos; 33%, three embryos; 3%,
two embryos; and less than 1%, one embryo. By 1998, the percentage
of cycles in which four or more embryos were transferred had
decreased to 33%; half of all ART cycles involved the transfer of
three embryos; 16% of cycles, two embryos; and less than 1%, one
embryo. By 2005, four or more embryos were transferred in only 4% of
cycles, three in 20% of cycles, two in more than two-thirds (72%)
of cycles, and one in 4% of cycles.
Figure 55: Percentages of Fresh–Nondonor
Cycles That Involved the Transfer of One, Two, Three, or
Four or More Embryos in Women Who Were Younger Than 35 and Set
Aside Extra Embryos for Future Use, 1996–2005.
Have there been improvements in
ART success rates, by number of embryos transferred?
Figure 56
presents success rates by the number of embryos transferred for ART
cycles using fresh nondonor eggs or embryos from 1996 through
2005. In general, success rates were higher when two or more embryos
were transferred. From 1996 through 2005, the success rates almost
tripled, from 14% to 41%, for ART cycles that involved the transfer
of two embryos. The success rates also increased for ART cycles that
involved the transfer of either one or three embryos; however, the
success rates decreased 13%, from 32% to 28%, for ART cycles that
involved the transfer of four or more embryos.
The relationship between number of embryos
transferred and success rates is complicated by several
factors, such as the woman’s age and embryo quality. Trends over
time may reflect changes in these factors.
Figure 56:
Percentages of Transfers (Using Fresh Nondonor Eggs or Embryos) That
Resulted in Live Births, by Number of Embryos Transferred, 1996–2005.
Have there been improvements in
the percentage of transfers that resulted in live births for women
younger than 35 who have more embryos available than they choose to
transfer?
Figure 57 shows changes over time
in the number of embryos transferred and the percentage of transfers
that resulted in live births for ART cycles in which the woman was
younger than 35 and chose to set aside some embryos for future
cycles rather than transfer all available embryos at one time.
Previous research suggests that the number of embryos available for
an ART cycle is an important predictor of success. Younger women
also tend to have higher success rates (see
Figure 14).
For this group of women, the percentage of transfers
that resulted in live births generally increased over time,
regardless of the number of embryos transferred. The biggest
increase was for cycles in which two embryos were transferred. In
1996, the chance for a live birth was highest (41%) when three
embryos were transferred; however, in 2005, the chance for a live
birth was highest (53%) when two embryos were transferred.
Success rates for cycles involving the transfer of
one embryo were comparable to those that involved multiple embryos.
Elective single-embryo transfer minimizes the risk for
multiple-infant pregnancy and related adverse outcomes. Recently,
the Society for Assisted Reproductive Technology (SART)
revised its embryo transfer guidelines to encourage single-embryo
transfer among patients with good prognoses.
Figure 57:
Percentages of Transfers That Resulted in Live Births Among Women
Who Were Younger Than 35 and Set Aside Extra Embryos for Future Use,
by Number of Embryos Transferred, 1996–2005.
Has the percentage of
multiple-infant live births changed?
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. Figure
58
shows the percentages of multiple-infant live births for the four
primary types of ART procedures.
For fresh-nondonor ART cycles, the percentage of
multiple-infant live births decreased 17% since 1996, from 38% of
all live births in 1996 to 32% in 2005. Over the same time period,
the percentage of multiple-infant live births decreased 16% for
frozen–nondonor cycles and 2% for fresh-donor cycles. In all years
except 1997, the percentage of multiple-infant live births remained
stable for frozen-donor cycles.
Figure 58:
Percentages of ART Cycles That Resulted in Multiple-Infant Live
Births, by Type of ART Cycle, 1996–2005.
Have multiple-infant live births
for cycles using fresh nondonor eggs or embryos changed for all ART
patients or only for those in particular age groups?
Figure 59 shows
that the percentages of multiple-infant live births decreased
between 1996 and 2005 for women in all age groups. In 1996, 43% of
live-birth deliveries to women younger than 35 were multiple-infant
births, compared with 36% in 2005. Among women older than 42, the
percentages of multiple-infant live births decreased slightly, from
14% in 1996 to 13% in 2005.
Figure 59:
Percentages of Multiple-Infant Live Births,
for Fresh–Nondonor Cycles, by ART Patient’s Age, 1996–2005.
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