Preimplantation Genetic Testing Improves IVF Outcomes

Preimplantation genetic testing for aneuploidy (PGT-A) can mitigate the negative effects of maternal age on in vitro fertilization (IVF) outcomes by selecting normal embryos that are more likely to lead to sustained implantation, according to a study published in the July issue of Fertility and Sterility.

“Our findings provide evidence that successful IVF outcomes can be achieved without multiple-embryo transfer when transfers are combined with the use of single nucleotide polymorphism-based PGT-A,” write the authors led by Alexander Simon, from Natera in San Carlos, Calif. “We hope that these findings will allay both patient anxiety about the possibility of miscarrying a single transferred embryo (i.e., without a “backup”) and physician concern about reduced pregnancy rates.”

IVF outcomes remain low, with fewer than half of all transferred embryos leading to a successful pregnancy in the United States. Aneuploidy—embryos with an abnormal number of chromosomes—is the leading cause of failed IVF. It is hoped that PGT-A can improve IVF outcomes, but data has been limited to date.

In what is thought to be the largest study of pregnancy outcomes in women undergoing IVF guided by the use of single nucleotide polymorphism- (SNP-) based PGT-A, researches evaluated outcomes in 974 women (aged 20 to 46 years) undergoing IVF treatment (1,883 IVF cycles from Oct.1, 2010, to Aug. 31, 2013) at Pacific Fertility Center (PFC; San Francisco, Calif.) and Conceptions Reproductive Associates of Colorado (CRA; Litteton). Elective PGT-A was performed using a 24-chromsome SNP assay (Spectrum PGT-A; Natera) on three to eight trophectoderm cells from high- and medium-grade embryos on culture day 5 or 6. Biopsy samples were processed and shipped overnight to Natera’s CLIA-certified lab.

Overall, 53 percent of IVF cycles were tested with PGT-A. Interesting, PGT-A uptake differed by site, with CRA performing PGT-A on 81.3 percent of cycles (881 of 1,084) versus 40.5 percent at PFC (1,002 of 2,470).

The researchers found that aneuploidy was detected in 42.9 percent of blastocysts from nondonor cycles. The proportion of aneuploid blastocysts increased with maternal age, from 26.9 percent in women younger than 35 years of age to more than 70 percent in women over 40 years of age.

Using PGT-A-guided embryo selection, the fertility clinics observed an implantation rate of 69.9 percent, clinical pregnancy rate per transfer of 70.6 percent, and live birth rate per transfer of 64.5 percent in 1,621 nondonor frozen cycles. In addition, PGT-A-related outcomes remained relatively constant across all maternal ages. There were no statistically significant differences in pregnancy outcomes for single-embryo transfers versus double-embryo transfers using PGT-A-selected embryos.

“[The] rapid increase in aneuploidy and decrease in the probability of obtaining euploid embryos after the age of 35 years, underscore the importance of accurate identification and selective transfer of euploid embryos in women of advanced maternal age undergoing IVF treatment,” writes Simon and colleagues.

Takeaway: PGT-A-guided embryo selection improves IVF outcomes, even in women with advanced age and using single-embryo transfers.