Section 5: ART Trends 1999-2008

Figure 51 shows the number of ART cycles performed, live-birth deliveries, and infants born using ART from 1999 through 2008. The number of ART cycles performed in the United States has nearly doubled, from 87,636 cycles in 1999 to 148,055 in 2008. The number of live-birth deliveries in 2008 (46,326) was more than two times higher than in 1999 (21,746). The number of infants born who were conceived using ART also increased steadily between 1999 and 2008. In 2008, 61,426 infants were born, which was more than two times higher than the 30,629 born in 1999. 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.

Intracytoplasmic sperm injection (ICSI) was originally developed to use in ART cycles to improve fertilization rates when severe male factor infertility was the indication for using ART. Today, this procedure is widely used even among couples without a diagnosis of male factor infertility.

Figure 52 shows the number of ART cycles performed using ICSI from 1999 through 2008. Overall, the number of ART cycles with ICSI procedures continued to increase for all fresh cycles. During the past 10 years, the number of fresh nondonor cycles performed with ICSI more than doubled, from 28,090 in 1999 to 67,328 in 2008. The number of fresh donor cycles with ICSI more than tripled, from 2,623 to 8,088 over the same period.

The number of frozen cycles (with or without ICSI) also more than doubled, from 12,178 in 1999 to 25,261 in 2008 for frozen nondonor cycles and from 2,605 to 6,344 for frozen donor cycles over the same period.

Note that the information on use of ICSI is not consistently collected across clinics for ART cycles using frozen embryos; therefore, these cycles are presented together as one group.

Figure 53 presents percentages of transfers that resulted in live births for ART cycles with or without ICSI. Percentages of transfers that resulted in live births are presented rather than percentages of cycles that resulted in live births because this is the only way to directly compare cycles using fresh embryos with those using frozen embryos.

In general, with or without ICSI, fresh donor cycles had the highest success rates when compared with fresh nondonor cycles or frozen cycles. However, when comparing success rates within each type of ART cycle, the percentage of transfers that resulted in live births among cycles without ICSI remained slightly higher than cycles with ICSI from 1999–2008.

The percentage of transfers that resulted in live births for cycles using fresh donor embryos without ICSI increased from 43% in 1999 to 58% in 2008, while cycles using fresh donor embryos with ICSI increased from 40% to 54% over the same period. Similar to trends with cycles using fresh nondonor embryos, the percentage of transfers that resulted in live births for fresh nondonor cycles with ICSI increased from 30% in 1999 to 36% in 2008, but was generally lower than the cycles without ICSI (32% in 1999 to 38% in 2008).

Note that the information on use of ICSI is not consistently collected across clinics for ART cycles using frozen embryos; therefore, these cycles are presented together as one group.

Singleton live births are an important measure of success because they entail a much lower risk than multiple-infant births for adverse infant health outcomes, including prematurity, low birth weight, disability, and death. Figure 54 shows that the percentage of transfers that resulted in singleton live births increased over time for all ART cycles with or without ICSI.

Although the total number of nondonor cycles using ICSI increased over the past 10 years (see Figure 52), percentages of transfers that resulted in singleton live births from these cycles were not any higher than those without ICSI.

Overall, percentages of transfers that resulted in singleton live births were consistently higher for fresh donor cycles than for fresh nondonor cycles and frozen cycles. Fresh donor cycles without ICSI increased from 25% in 1999 to 34% in 2008; a similar increase was observed for fresh donor cycles with ICSI. Over the same period, the percentage of transfers that resulted in singleton live births increased from 20% to 26% for fresh nondonor cycles without ICSI and from 19% to 25% with ICSI.

Note that the information on use of ICSI is not consistently collected across clinics for ART cycles using frozen embryos; therefore, these cycles are presented together as one group.

Figure 55 presents percentages of transfers that resulted in live births, by the age of the woman, for ART cycles using fresh nondonor eggs or embryos.

From 1999 through 2008, the percentage of transfers that resulted in live births for women younger than age 35 increased 25%, from 38% in 1999 to 47% in 2008. Over the same period, the percentage of transfers that resulted in live births increased 15% (from 32% to 37%) for women aged 35–37 years, 16% (from 24% to 28%) for women 38–40, and 21% (from 14% to 16%) for women 41–42. Please note the percentage of transfers that resulted in live births were rounded to the nearest whole number while the percent changes were calculated using raw data.

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 56 presents percentages of transfers that resulted in singleton live births, by the age of the woman, for ART cycles using fresh nondonor eggs or embryos.

From 1999 through 2008, the percentage of transfers that resulted in singleton live births for women younger than 35 increased 36%, from 22% in 1999 to 30% in 2008. Over the same period, the percentage of transfers that resulted in singleton live births increased 26% (from 21% to 26%) for women 35–37, 22% (from 17% to 21%) for women 38–40, and 19% (from 12% to 14%) for women 41–42. Please note the percentage of transfers that resulted in singleton live births were rounded to the nearest whole number while the percent changes were calculated using raw data.

Figure 57 presents the trends for the number of embryos transferred in fresh nondonor cycles that progressed to the embryo transfer stage. From 1999 through 2008, cycles that involved the transfer of one embryo doubled, from 6% to 12%; cycles that involved the transfer of two embryos more than doubled, from 23% in 1999 to 50% in 2008. Cycles that involved the transfer of three embryos decreased from 34% in 1999 to 25% in 2008, and cycles that involved the transfer of four or more embryos decreased dramatically from 36% in 1999 to 14% in 2008.

As shown in Figure 57, the number of embryos transferred in fresh nondonor cycles has decreased during the past 10 years. Figure 58 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 percentages of ART cycles that result in pregnancies and live births (see Figure 15).

Overall, the number of embryos transferred decreased among couples who chose to transfer fewer embryos than were available. In 1999, approximately 19% of ART cycles involved the transfer of four or more embryos; 45%, three embryos; 35%, two embryos; and 1%, one embryo. By 2008, four or more embryos were transferred in less than 2% of cycles, three in 11% of cycles, two in 77% of cycles, and one in more than 10% of cycles.

Figure 59 presents percentages of transfers that resulted in live births, by the number of embryos transferred for ART cycles using fresh nondonor eggs or embryos from 1999 through 2008. The percentage of transfers that resulted in live births increased the most for ART cycles that involved the transfer of one or two embryos (12% to 22% and 31% to 44%, respectively). However, over the same period, there were no increases for ART cycles that involved the transfer of three embryos (remained about 35%) or four or more embryos (31% to 27%).

The relationship between the 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 60 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 percentages of ART cycles that result in pregnancies and live births (see Figure 15).

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, from 47% in 1999 to 57% in 2008.

Percentages of transfers that resulted in live births for cycles involving the transfer of one embryo were comparable to those that involved two or three embryos. Elective single-embryo transfer minimizes the risk for multiple-fetus pregnancy and related adverse outcomes. In 2009, the Society for Assisted Reproductive Technology (SART) revised its embryo transfer guidelines to encourage single-embryo transfer among patients with good prognoses. (For more information, contact SART by telephone at 205-978-5000 or online at www.sart.org.)

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 61 shows percentages of multiple-infant live births for the four primary types of ART procedures.

For fresh nondonor cycles, the percentage of multiple-infant live births decreased 14% since 1999, from 37% of all live births in 1999 to 32% in 2008. Over the same period, the percentage of multiple-infant live births decreased 15% for frozen nondonor cycles, 17% for frozen donor cycles, and 4% for fresh donor cycles.

Figure 62 shows that percentages of multiple-infant live births decreased between 1999 and 2006 and increased slightly after 2006 for women in age groups younger than 35 through women 38–40. In 1999, 41% of live-birth deliveries to women younger than 35 were multiple-infant births, compared with 35% in 2008. Among women aged 41–42 years, the percentage of multiple-infant live births increased from 15% in 1999 to 19% in 2002 and decreased to 16% in 2008.

Figure 63 presents the trends in percentages of transfers that resulted in live births and percentages of multiple-infant live births for ART cycles using fresh nondonor eggs or embryos. Overall, the percentage of transfers that resulted in live births increased from 31% in 1999 to approximately 37% in 2008. From 1999 through 2008, the percentage of singleton live births increased from 63% to 68%; the percentage of twin births remained stable, ranging from 30% to 32%; and the percentage of triplet-or-more births decreased considerably from 5% in 1999 to 2% in 2008.

It is important to note that twins, albeit to a lesser extent than triplets or more, are still at substantially greater risk for illness and death than singletons. These risks include low birth weight, preterm birth, and neurological impairments such as cerebral palsy. Both percentages of twin and triplet-or-more births remain significantly higher for ART births than for births resulting from natural conception.