Neal et al.
Fert Stert 2016; http://dx.doi.org/10.1016/j.fertnstert.2016.11.013
This study is based on the assumption that in quantitative PCR, the number of PCR cycles required to reach a signal threshold CT for a given genomic locus is inversely related to the amount of DNA at that locus. Thus, samples reaching the threshold at a lower cycle number than others contain more DNA. In the first phase of the study a standard curve was established using a euploid fibroblast cell line taking into account both known cell number as well as mean CT value. This curve then was used to estimate the DNA content of TE-biopsies (stratified in quartiles of DNA). Phase 2 of the study examined reproductive outcomes in patients undergoing single embryo transfer after trophectoderm biopsy and CCS. There were no differences among the four quartiles with respect to age, BMI, endometrial thickness, or the percentage of transfers in a frozen cycle. The last quartile of highest relative DNA content did have a significantly lower ongoing pregnancy rate and live birth rate when compared with the other three quartiles (49% vs. 64%). This stresses that the relative DNA content of TE biopsies is an important factor that can influence reproductive competence of embryos. In other words, both timing and size of biopsy are important variables when dealing with CCS.