What is the risk of having a multiple-fetus pregnancy or
multiple-infant live 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 or death.
Part A of Figure 39 shows that among
the 5,898 pregnancies that resulted from ART cycles using frozen
nondonor embryos, about 67% were singleton pregnancies, about 20% were
twins, and nearly 4% were triplets or more. Nine percent 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 what was reported (about 24%).
In 2004, 4,658 pregnancies from ART cycles that used frozen nondonor
embryos resulted in live births. Part B of
Figure 39 shows that approximately
24% of these live births produced more than one infant (about 22% twins
and 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 for 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 39: Risk of Having
Multiple-Fetus Pregnancy and Multiple-Infant Live Birth from ART Cycles
Using Frozen Nondonor Embryos, 2004.
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