2007 ART Report Section 2-ART Cycles Using Fresh, Nondonor Eggs or Embryos (Part C)

For about 37% of ART procedures that used fresh nondonor eggs or embryos in 2007, standard IVF (in vitro fertilization) techniques were used: eggs and sperm were combined in the laboratory, the resulting embryos were cultured for 2 or more days, and one or more embryos were then transferred into the woman’s uterus through the cervix.

For most of the remaining ART procedures (about 63%), fertilization was accomplished using intracytoplasmic sperm injection (ICSI). This technique involves injecting a single sperm directly into an egg; the embryos are then cultured and transferred as in standard IVF.

For a small proportion of ART procedures, unfertilized eggs and sperm (gametes) or early embryos (zygotes) were transferred into the woman’s fallopian tubes. These procedures are known as gamete and zygote intrafallopian transfer (GIFT and ZIFT). Some women with tubal infertility are not suitable candidates for GIFT and ZIFT. GIFT and ZIFT are more invasive procedures than IVF because they involve inserting a laparoscope into a woman’s abdomen to transfer the embryos or gametes into the fallopian tubes. In contrast, IVF involves transferring embryos or gametes into a woman’s uterus through the cervix without surgery.

Figure 28 shows the percentage of egg retrievals that resulted in a live birth for each type of ART procedure started in 2007. Percentages for the two predominant types of ART, IVF without ICSI and IVF with ICSI, were similar. Percentages of egg retrievals that resulted in live births for cycles that used GIFT, ZIFT, or a combination of IVF were lower than for cycles that used other ART procedures. See Figures 29–31 and Figures 50–55 for further details on IVF procedures that used ICSI.

ICSI was developed to overcome problems with fertilization that sometimes occur in couples diagnosed with male factor infertility. In 2007, 64,554 ICSI cycles were performed. Slightly less than half of the ICSI cycles were performed for couples with a diagnosis of male factor infertility. However, diagnostic procedures may vary from one clinic to another, so the categorization of causes of infertility may also vary.

ICSI was developed to overcome problems with fertilization that sometimes occur among couples diagnosed with male factor infertility. In 2007, 82% of couples diagnosed with male factor infertility used IVF with ICSI. Because ICSI can only be performed when at least one egg has been retrieved, Figure 30 presents percentages of retrievals that resulted in live births for these ICSI procedures among couples diagnosed with male factor infertility. For comparison, these percentages are presented alongside the percentages for ART cycles that used standard IVF without ICSI among couples with all diagnoses except male factor infertility.

For every age group, when ICSI was used for couples diagnosed with male factor infertility, percentages of retrievals that resulted in live births were similar to those achieved by couples who used standard IVF without ICSI and were not diagnosed with male factor infertility. Please note, however, the definitions of infertility diagnoses may vary from clinic to clinic and that a review of select clinical records revealed that reporting of infertility causes may be incomplete. (See Findings from Validation Visits for 2007 ART Data in Appendix A for additional information.) Therefore, differences in success rates by causes of infertility should be interpreted with caution.

As shown in Figure 29, a large number of ICSI procedures are now performed even when couples are not diagnosed with male factor infertility. Figure 31 presents percentages of egg retrievals that resulted in live births for those cycles compared with ART cycles among couples who used IVF without ICSI. For every age group, the ICSI procedures were less successful. Please note, however, the definitions of infertility diagnoses may vary from clinic to clinic and that a review of select clinical records revealed that reporting of infertility causes may be incomplete. (See Findings from Validation Visits for 2007 ART Data in Appendix A for additional information.) Additionally, information was not available to determine whether this finding was a direct effect of the ICSI procedure or whether the patients who used ICSI were somehow different from those who use IVF alone. Therefore, differences in success rates by causes of infertility should be interpreted with caution.

Figure 32 shows that approximately 40% of ART cycles that used fresh nondonor eggs or embryos and progressed to the embryo transfer stage in 2007 involved the transfer of three or more embryos, about 14% of cycles involved the transfer of four or more, and approximately 5% of cycles involved the transfer of five or more embryos.

Figure 33 shows the relationship between the number of embryos transferred during an ART procedure in 2007 and the number of infants born alive as a result of that procedure. The percentage of transfers that resulted in live births increased when two or more embryos were transferred; however, transferring multiple embryos also poses a risk of having a multiple-infant birth. Multiple-infant births cause concern because of the additional health risks they create for both mothers and infants. Also, pregnancies with multiple fetuses are potentially subject to multifetal reduction. Multifetal reduction can happen naturally (e.g., fetal death), or a woman or couple may decide to reduce the number of fetuses using a procedure called multifetal pregnancy reduction. Information on multifetal pregnancy reductions is incomplete and therefore is not provided here.

The relationships between number of embryos transferred, percentages of transfers resulting in live births, and multiple-infant births are complicated by several factors, such as the woman’s age and embryo quality. See Figure 34 for more details on women most at risk for multiple births.

Although, in general, transferring more than one embryo tends to improve the chance for a successful ART procedure (see Figure 33), other factors are also important. Previous research suggests that the number of embryos fertilized and thus available for ART is just as, if not more, important in predicting success as the number of embryos transferred. Additionally, younger women tend to have both higher percentages of live births and higher likelihood of multiple-infant births. Figure 34 shows the relationship between the number of embryos transferred, percentages of transfers resulting in live births, and multiple-infant births for a subset of 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.

For this group, the chance for a live birth using ART was about 50% when only one embryo was transferred. If one measures success as the percentage of transfers resulting in singleton live births, the highest likelihood of live birth was observed with only one embryo transferred.

The proportion of live births that were multiple-infant births was about 41% with two embryos and about 45% with three embryos. Transferring three or more embryos also created an additional risk for higher-order multiple births (i.e., triplets or more).

Once an ART cycle has progressed from egg retrieval to fertilization, the embryo(s) can be transferred into the woman’s uterus in the subsequent 1 to 6 days. Figure 35 shows that in 2007 approximately 59% of embryo transfers occurred on day 3. Day 5 embryo transfers were the next most common, accounting for about 31% of ART procedures that progressed to the embryo transfer stage.

As shown in Figure 35, in the vast majority of ART procedures, embryos were transferred on day 3 (59%) or day 5 (31%). Figure 36 compares percentages of day 3 embryo transfers that resulted in live births with those for day 5 embryo transfers. In all age groups, percentages were higher for day 5 embryo transfers than for day 3 transfers. However, some cycles do not progress to the embryo transfer stage because of embryo arrest (interruption in embryo development) between day 3 and day 5. These cycles are not accounted for in percentages of day 5 transfers that resulted in live births. Therefore, differences in percentages of day 3 and day 5 transfers that result in live births should be interpreted with caution.

Figure 37 shows the number of embryos transferred on day 3 and day 5. Overall, fewer embryos were transferred on day 5 than on day 3. Approximately 51% of day 3 embryo transfers and 21% of day 5 embryo transfers involved the transfer of three or more embryos. The decrease in the number of embryos transferred on day 5; however, did not translate into a lower risk for multiple-infant births. See Figure 38 for more details on the relationship between multiple-infant birth risk and day of embryo transfer.

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 38 shows that among the 15,611 live births that occurred following day 3 embryo transfer, about 72% were singletons, 27% were twins, and 2% were triplets or more. Thus, approximately 29% of these live births produced more than one infant.

In 2007, 11,799 live births occurred following day 5 embryo transfer. Part B of Figure 38 shows that approximately 36% of these live births produced more than one infant (34% twins and 2% triplets or more).

As shown in Figure 37, fewer embryos were transferred on day 5 than on day 3. However, the proportion of live births resulting in twins is higher among transfer procedures performed on day 5 than on day 3. Thus, the risk of having a multiple-infant birth was higher for day 5 embryo transfers. The likelihood of multiple-infant births for both day 3 and day 5 embryo transfers is much higher overall than for multiple-infant births in the general U.S. population (about 3%).

As shown in Figure 37 and 38, embryos transferred on day 5 result in more multiple-infant births compared with embryos transferred on day 3, despite the smaller number of embryos transferred on day 5. Figure 39 shows the relationship between the number of embryos transferred, the percentage of transfers resulting in live births, and the percentage of multiple-infant births for day 5 embryo transfer procedures in which the woman was younger than 35 and the couple decided to set aside some embryos for future cycles rather than transfer all available embryos at one time.

The percentage of transfers resulting in live births was the highest (about 60%) when two embryos were transferred; however, the proportion of live births that were multiples (twins or more)—which presents a higher risk for poor health outcomes—was 45%. The percentage of live births that were higher-order multiples (triplets or more) was much higher when 3 or more embryos were transferred on day 5 (almost 9%) than for those involving the transfer of just two embryos on day 5 (1%).

If one measures success as the percentage of transfers resulting in singleton live births, the highest percentage (52%) was observed with the transfer of a single embryo on day 5.

In some cases a woman has trouble carrying a pregnancy. In such cases the couple may use ART with a gestational carrier, sometimes called a surrogate. A gestational carrier is a woman who agrees to carry the developing embryo for a couple with infertility problems. Gestational carriers were used in 1% of ART cycles using fresh nondonor embryos in 2007 (733 cycles). Figure 40 compares percentages of transfers that resulted in live births for ART cycles that used a gestational carrier in 2007 with cycles that did not. In most age groups, percentages of transfers that resulted in live births for ART cycles that used gestational carriers were higher than for those cycles that did not.

The number of ART procedures performed every year varies among fertility clinics in the United States. In 2007, percentages of ART cycles that resulted in live births were similar for all 430 clinics regardless of the number of cycles performed. For Figure 41, clinics were divided equally into four groups (called quartiles) based on the size of the clinic as determined by the number of ART cycles it performed. The percentage for each quartile represents the average percentage of ART cycles that resulted in live births for clinics in that quartile. For the exact number of cycles and percentage at an individual clinic, refer to the clinic table section of this report.