Section 4: ART Cycles Using Donor Eggs
As shown in Figures 15–17, eggs produced by women in older age groups form embryos that are less likely to implant and more likely to result in miscarriage if they do implant. As a result, ART using donor eggs is much more common among older women than among younger women. Donor eggs or embryos were used in approximately 12% of all ART cycles performed in 2008 (18,121 cycles). Figure 46 shows the percentage of ART cycles using donor eggs in 2008 according to the woman’s age. Few women younger than age 40 used donor eggs; however, the percentage of cycles performed with donor eggs increased sharply starting at age 40. Among women older than age 48, for example, 90% of all ART cycles used donor eggs.
Do percentages of transfers that result in live births differ by age for women who used ART with donor eggs compared with women who used ART with their own eggs?
Figure 47 compares percentages of transfers that resulted in live births for ART cycles using fresh embryos from donor eggs with those for ART cycles using a woman’s own eggs, among women of different ages. The likelihood of a fertilized egg implanting is related to the age of the woman who produced the egg. Thus, the percentage of transfers resulting in live births for cycles using embryos from women’s own eggs declines as women get older. In contrast, since egg donors are typically in their 20s or early 30s, the percentage of transfers that resulted in live births for cycles using embryos from donor eggs remained consistently high at above 50% for most patients aged 24 or older.
Figure 48 shows percentages of transfers that resulted in live births and singleton live births for ART cycles using fresh embryos from donor eggs among women of different ages. For all ages, the percentage of transfers that resulted in singleton live births (average 33%) was lower than the percentage of transfers that resulted in live births (average 55%). 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.
What is the risk of having a multiple-fetus pregnancy or multiple-infant live birth from an ART cycle using fresh donor eggs?
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 49 shows that among the 6,843 pregnancies that resulted from ART cycles using fresh embryos from donor eggs, approximately 52% were singleton pregnancies, 39% were twins, and more than 3% were triplets or more. About 5% of pregnancies ended 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 (approximately 42%).
In 2008, 5,894 pregnancies from ART cycles that used fresh embryos from donor eggs resulted in live births. Part B of Figure 49 shows that almost 40% of these live births produced more than one infant. This compares with a multiple-infant birth rate of slightly more than 3% in the general U.S. population.
Although total percentages 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. CDC does not collect information on multifetal pregnancy reductions..
How do percentages of transfers that result in live births differ for ART cycles between women who use frozen donor embryos and those who use fresh donor embryos?
Figure 50 shows that percentages of transfers that resulted in live births and singleton live births for ART cycles using frozen donor embryos were substantially lower than for ART cycles using fresh donor embryos. The average number of embryos transferred was similar for cycles using frozen donor embryos and those using fresh donor embryos. (See the national summary table for information on the average number of embryos transferred for these cycles.)