Prediction of embryo euploidy and pregnancy outcome by blastocyst morphology and development speed for women receiving single embryo transfer

Abstract

Background

Selection of high-quality blastocysts is the most important factor determining the success of assisted reproductive technology. The objective of this study is to assess the values of blastocyst morphological quality and development speed for predicting euploidy and clinical pregnancy outcome.

Methods

A total of 155 preimplantation genetic testing cycles including 959 blastocysts and 154 euploid blastocyst transfer cycles conducted between January 2018 and December 2019 were retrospectively analysed. The associations of blastocyst morphological quality and development speed (D) with chromosomal status, clinical pregnancy rate, early miscarriage rate, and ongoing pregnancy rate were evaluated by univariate and multivariate regression.

Results

The euploidy rate of development speed D5 blastocysts was significantly greater than that of D6 blastocysts (61.4% vs. 38.1%, P < 0.001), and the euploid rate of morphologically high-grade blastocysts was significantly greater than that of non-high-grade blastocysts. Development speed D5 (OR = 1.6, 95% CI 1.2–2.2, P = 0.02) and high-grade morphology (OR = 2.1, 95% CI 1.5–2.9, P = 0.01) were independent predictors of euploidy. The ongoing pregnancy rate of D5 blastocysts was significantly higher than that of D6 blastocysts (62.3% vs. 43.8%, P = 0.04). Transfer of euploid blastocysts with high-grade morphology resulted in a greater ongoing pregnancy rate than transfer of non-high-grade euploid blastocysts (60.7% vs. 43.2%, P = 0.049). Alternatively, D6 development speed was an independent risk factor for early pregnancy loss after euploid blastocyst transfer. Multivariate regression analysis adjusting for confounding factors identified maternal age, blastocyst development speed, and blastocyst morphological grade as independent predictors of euploidy but not of clinical pregnancy.

Conclusion

The recommended sequence of embryo transfer based on the present study is D5 high-grade > D6 high-grade > D5 non-high-grade > D6 non-high-grade.

PLAIN LANGUAGE SUMMARY

Assisted reproductive technology physicians are actively exploring methods to improve the accuracy of embryo selection for successful pregnancy. We evaluated the associations of embryo morphological grade and development speed with chromosomal status and clinical outcome for couples without a history of infertility, in vitro fertilisation failure, or recurrent miscarriage receiving euploid embryo transfer. Blastocysts from females younger than 35 years, of high morphological grade, and demonstrating faster development speed were most likely to be euploid (least likely to have chromosomal abnormalities). Alternatively, patients implanted with slower developing euploid blastocysts were at higher risk of early pregnancy loss. To maximise the probability of implanting euploid embryos and minimise the risk of pregnancy loss, the selection order of embryo transferred should be based on embryo development speed followed by morphological grades.

Keywords:

• Preimplantation genetic testing
• blastocyst morphology
• euploidy
• clinical pregnancy rate
• ongoing pregnancy rate

Acknowledgments

We thank all study participants and staff of the Centre of Reproductive Medicine for their support.

Authors’ contributions

KD and LL conceived and designed the study. KD and CW analysed the data. KD and LL wrote the first draft of the manuscript and revised it. XH and YZ participated in study implementation and manuscript revision. All authors have read and approved the final manuscript.

Data availability statement

Data supporting the results of this study will be shared upon reasonable request to the corresponding author.

Additional information

Funding

This work was supported by Science and Technology Project of Guangzhou (Key research and development plan) [No. 2024B03J1251], Natural Science Foundation of Guangdong Province [No. 2024A1515011168], and the National Natural Science Foundation of China [No. 81871159].