2001 Assisted Reproductive Technology (ART) Report: Section
3, ART Cycles Using Frozen Nondonor Embryos |
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What are the success rates for ART cycles using frozen nondonor embryos?
Frozen
embryos were used in approximately 14% of all ART cycles performed in 2001
(14,075 cycles). Figure 33
compares the success rates for frozen embryos with the success rates for
fresh embryos among women using their own eggs. Because some embryos do
not survive the thawing process, the live birth per thaw rate is usually
lower than the live birth per transfer rate. In 2001, the success rates
for frozen embryos were lower than the success rates for fresh embryos.
However, the average number of embryos transferred was similar for cycles
using both frozen embryos and fresh embryos (see the
national summary
table for information on the average number of embryos
transferred for these cycles). It is important to note that cycles using
frozen embryos are both less expensive and less invasive than those using
fresh embryos because the woman does not have to go through the fertility
drug stimulation and egg retrieval steps again.
Figure
33: Success Rates for ART Cycles Using Frozen Embryos and Fresh
Embryos, 2001.
What is the risk of
having a multiple-fetus pregnancy or multiple-infant birth from an ART
cycle using frozen nondonor embryos?
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 and death.
Part A of
Figure 34 shows that among the
3,850 pregnancies that resulted from ART cycles using frozen nondonor
embryos, 66% were singleton pregnancies, about 22% were twin pregnancies,
and slightly more than 4% were triplet or greater pregnancies. Almost 8%
of pregnancies ended in miscarriage before the number of fetuses could be
accurately determined. Therefore, the percentage of pregnancies with more
than one fetus might have been higher than the 27% reported.
In 2001,
3,075 pregnancies from ART cycles that used frozen nondonor embryos
resulted in live births. Part B of
Figure 33 shows that approximately 27% of these live births produced
more than one infant (24.2% twins and 2.6% triplets or more). This
compares with a multiple-infant birth rate of 3% in the general U.S.
population.
Although
the total rates for multiples were the same for pregnancies and live
births, there were more triplet pregnancies than triplet 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
34: Risk of Having Multiple-Fetus Pregnancy and Multiple-Infant Live
Birth from ART Cycles Using Frozen Nondonor Embryos, 2001.
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:
03/27/2006
Content source: Division
of Reproductive Health,
National Center for Chronic Disease
Prevention and Health Promotion
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