Association between growth dynamics, morphological parameters, the chromosomal status of the blastocysts, and clinical outcomes in IVF PGS cycles with single embryo transfer

Abstract

Purpose: The purpose of the present study is to examine interconnection between speed of embryo development, the genetic status of the blastocysts, and clinical outcomes in IVF preimplantation genetic screening (PGS) cycles with single embryo transfer (SET).

Methods: The retrospective comparative study has been performed between January 2013 and January 2016. Seven hundred thirty-seven cycles of IVF treatment with PGS, followed by 503 SETs, were included in the study. Normally fertilized oocytes were hatched on day 3, were cultured to the blastocyst stage, and were biopsied only when at least three to seven cells were herniating from zona pellucida on the morning of day 5 (≤118 h) or day 6 (≥139 h). A total of 3705 embryos were analyzed for euploidy rates and blastocyst morphology. All embryos were vitrified after the biopsy, and selected embryos were subsequently thawed for a hormone replacement frozen embryo transfer cycle.

Results: The euploidy rate was significantly higher among embryos biopsied on day 5 versus day 6: 59.44 ± 4.1 and 48.19 ± 3.8, respectively, p < 0.05. The difference in euploidy rates between embryos biopsied on day 5 versus day 6 in matched age groups increased from 5.83 to 25.46% with advancing maternal age. Our data demonstrated no statistically significant difference in euploidy rates between good-quality embryos biopsied on day 5 in the group of patients <38 years old and embryos in PGS cycles using donor oocytes: 71.12% (336/472) and 75.68% (221/292), respectively, p = 0.174, χ ² = 1.848. In 270 out of 503 SETs, transferred embryos were biopsied on day 5 (ongoing pregnancy rate was 64.6% in a group of patients <38 years old, and in a group of patients ≥38 years old, ongoing PR was 64.2%). In 233 out of 503 cycles, transferred embryos were biopsied on day 6 (ongoing PR was 46.6% in a group of patients <38 years old, and in a group of patients ≥38 years old, ongoing PR was 50.8%). In all study groups, the ongoing pregnancy rate was higher when the transferred embryo was available for biopsy on day 5.

Conclusions: Good- and fair-quality embryos available for biopsy on day 5 have higher euploidy rates and have a higher chance to result in an ongoing pregnancy. Euploidy rate has significant variations within the same age group depending on the morphology of the blastocysts.

Keywords: Blastocyst biopsy; Blastocyst morphology; CCS; Embryo development; Euploidy rates; IVF; Preimplantation genetic screening.

Fig. 1

Distribution of embryos for biopsy (left) and comparison of euploidy rates (right) between embryos biopsied on day 5 and day 6 in matched age groups

Fig. 2

Distribution of embryos in PGS cycles by embryo quality biopsied on day 5 (left) and on day 6 (right) in matched age groups

Fig. 3

Comparison of euploidy rates of good-, fair-, borderline fair-, and poor-quality blastocysts in matched age group

Fig. 4

Comparison of ongoing pregnancy rates after single embryo transfer of day 5 versus day 6 euploid embryo

Fig. 5

Comparison of ongoing pregnancy rates after transferring good-, fair-, and borderline fair-quality embryos available for the biopsy on day 5 versus day 6