As shown in Figures 12, 13, and 14, eggs produced by women in older age groups form embryos that are less likely to implant and more likely to spontaneously abort 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 carried out in 2004 (15,175 cycles). Figure 40 shows the percentage of ART cycles using donor eggs in 2004 according to the woman’s age. Few women younger than age 39 used donor eggs; however, the percentage of cycles carried out with donor eggs increased sharply starting at age 39. Among women older than age 47, about 91% of all ART cycles used donor eggs.

Figure 41 compares live birth rates 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. Egg donors are typically in their 20s or early 30s. Thus, the live birth per transfer rate for cycles using embryos from donor eggs varies only slightly across all age groups. The average live birth per transfer rate is 51%. In contrast, the live birth rates for cycles using embryos from women’s own eggs decline steadily as women get older.

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 43 shows that among the 5,449 pregnancies that resulted from ART cycles using fresh embryos from donor eggs, about 53% were singleton pregnancies, about 37% were twins, and nearly 5% were triplets or more. About 5% 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 42%).

In 2004, 4,690 pregnancies from ART cycles that used fresh embryos from donor eggs resulted in live births. Part B of Figure 43 shows that 40% of these live births produced more than one infant (about 38% twins and about 2% triplets or more). This compares with a multiple-infant birth rate of slightly more than 3% in the general 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 44 shows that the success rates per transfer for frozen donor embryos were substantially lower than the success rates per transfer for fresh donor embryos. This is similar to the findings for frozen nondonor embryos (see Figure 38). 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.)

Figure 44: Success Rates for ART Cycles Using Frozen Donor and Fresh Donor Embryos, 2004.