Live birth rate with conventional IVF shown noninferior to that with PGT-A
Yan J, Qin Y, Zhao H, et al. Live birth with or without preimplantation genetic testing for aneuploidy. N Engl J Med. 2021;385:2047-2058.
Preimplantation genetic testing for aneuploidy (PGT-A) is increasingly used in many in vitro fertilization (IVF) cycles in the United States. Based on data from the Centers for Disease Control and Prevention, 43.8% of embryo transfers in the United States in 2019 included at least 1 PGT-A–tested embryo.6 Despite this widespread use, however, there are still no robust clinical data for PGT-A’s efficacy and safety, and the guidelines published by the ASRM do not recommend its routine use in all IVF cycles.7 In the past 2 to 3 years, several large studies have raised questions about the reported benefit of this technology.8,9
Details of the trial
In a multicenter, controlled, noninferiority trial conducted by Yan and colleagues, 1,212 subfertile women were randomly assigned to either conventional IVF with embryo selection based on morphology or embryo selection based on PGT-A with next-generation sequencing. Inclusion criteria were the diagnosis of subfertility, undergoing their first IVF cycle, female age of 20 to 37, and the availability of 3 or more good-quality blastocysts.
On day 5 of embryo culture, patients with 3 or more blastocysts were randomly assigned in a 1:1 ratio to either the PGT-A group or conventional IVF. All embryos were then frozen, and patients subsequently underwent frozen embryo transfer of a single blastocyst, selected based on either morphology or euploid result by PGT-A. If the initial transfer did not result in a live birth, and there were remaining transferable embryos (either a euploid embryo in the PGT-A group or a morphologically transferable embryo in the conventional IVF group), patients underwent successive frozen embryo transfers until either there was a live birth or no more embryos were available for transfer.
The study’s primary outcome was the cumulative live birth rate per randomly assigned patient that resulted from up to 3 frozen embryo transfer cycles within 1 year. There were 606 patients randomly assigned to the PGT-A group and 606 randomly assigned to the conventional IVF group.
In the PGT-A group, 468 women (77.2%) had live births; in the conventional IVF group, 496 women (81.8%) had live births. Women in the PGT-A group had a lower incidence of pregnancy loss compared with the conventional IVF group: 8.7% versus 12.6% (absolute difference of -3.9%; 95% confidence interval [CI], -7.5 to -0.2). There was no difference in obstetric and neonatal outcomes between the 2 groups. The authors concluded that among women with 3 or more good-quality blastocysts, conventional IVF resulted in a cumulative live birth rate that was noninferior to that of the PGT-A group.
Some benefit shown with PGT-A
Although the study by Yan and colleagues did not show any benefit, and even a possible reduction, with regard to cumulative live birth rate for PGT-A, it did show a 4% reduction in clinical pregnancy loss when PGT-A was used. Furthermore, the study design has been criticized for performing PGT-A on only 3 blastocysts in the PGT-A group. It is quite conceivable that the PGT-A group would have had more euploid embryos available for transfer if the study design had included all the available embryos instead of only 3. On the other hand, one could argue that if the authors had extended the study to include all the available embryos, the conventional group would have also had more embryos for transfer and, therefore, more chances for pregnancy and live birth.
It is also important to recognize that only patients who had at least 3 embryos available for biopsy were included in this study, and therefore the results of this study cannot be extended to patients with fewer embryos, such as those with diminished ovarian reserve.
In summary, based on this study’s results, we may conclude that for the good-prognosis patients in the age group of 20 to 37 who have at least 3 embryos available for biopsy, PGT-A may reduce the miscarriage rate by about 4%, but this benefit comes at the expense of about a 4% reduction in the cumulative live birth rate. ●
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Despite the lack of robust evidence for efficacy, safety, and cost-effectiveness, PGT-A has been widely adopted into clinical IVF practice in the United States over the past several years. A large randomized controlled trial has suggested that, compared with conventional IVF, PGT-A application may actually result in a slightly lower cumulative live birth rate, while the miscarriage rate may be slightly higher with conventional IVF.
PGT-A is a novel and evolving technology with the potential to improve embryo selection in IVF; however, at this juncture, there is not enough clinical data for its universal and routine use in all IVF cycles. PGT-A can potentially be more helpful in older women (>38–40) with good ovarian reserve who are likely to have a larger cohort of embryos to select from. Patients must clearly understand this technology’s pros and cons before agreeing to incorporate it into their care plan.