Lower chromosomal abnormality frequencies in miscarried conceptuses from frozen blastocyst transfers in ART
Authors: Li Jing , Zhang Fuli , Sun Bo , Dai Shanjun , Yang Qingling , Hu Linli , Shi Hao , Xu Jiawei , Niu Wenbin , Guo Yihong 
Published: November 2020

Abstract

STUDY QUESTION
Are blastocyst culture and cryopreservation in ART associated with chromosomal abnormalities in miscarried products of conception (POC)?

SUMMARY ANSWER
Frozen blastocyst transfer in women aged 35 years or older and frozen embryo transfer (ET) (including both cleavage-stage embryo and blastocyst) in women aged &lt;35 years are associated with decreased frequencies of embryonic chromosomal abnormalities in miscarried POC.

WHAT IS KNOWN ALREADY
Blastocyst culture and embryo cryopreservation have been previously associated with favorable ART treatment outcomes and widely applied in clinical practice. However, the association between these embryo manipulation procedures and embryonic chromosomal abnormalities has not been evaluated to the best of our knowledge.

STUDY DESIGN, SIZE, DURATION
This retrospective study included a total of 720 patients who underwent IVF/ICSI, and the retained POC were obtained. A single-nucleotide polymorphism (SNP)-based chromosomal microarray analysis (CMA) of all miscarried conceptuses was performed.

PARTICIPANTS/MATERIALS, SETTING, METHODS
This study was based on the Clinical Reproductive Medicine Management System/Electronic Medical Record Cohort Database (CCRM/EMRCD) at our center. In total, 720 miscarried POCs were collected from patients undergoing ART (including fresh cleavage-stage ET, fresh blastocyst transfer, frozen cleavage-stage ET and frozen blastocyst transfer), and the incidences and profiles of cytogenetic abnormalities in the miscarried conceptuses were measured via SNP-based CMA.

MAIN RESULTS AND THE ROLE OF CHANCE
The chromosomal abnormality rate in POC varied from 33.7% to 66.7% among the different ET strategies. In the patients aged ≥35 years, frozen blastocyst transfer was significantly associated with a lower incidence of chromosomal aberrations in the POCs (adjusted odds ratio (aOR): 0.171 (95% CI: 0.040–0.738); P = 0.018) than fresh blastocyst transfer. In the patients aged &lt;35 years, frozen ET was significantly associated with a lower incidence of chromosomal aberrations than fresh ET in both cleavage-stage ET cycles and blastocyst transfers cycles (aOR: 0.545 (0.338–0.879), P = 0.013; and aOR: 0.357 (0.175–0.730), P = 0.005, respectively). Trisomy was the most frequent abnormal embryonic karyotype in the different ET strategies, and its frequency significantly differed among strategies (P &lt; 0.05).

LIMITATIONS, REASONS FOR CAUTION
This study was retrospectively designed, and we cannot draw any definite conclusions from our results regarding the adequate safety of embryo cryopreservation in ongoing pregnancy.

WIDER IMPLICATIONS OF THE FINDINGS
To our knowledge, this is the first study assessing the associations of ET strategies with the probability of miscarriage associated with embryonic chromosomal abnormalities. However, the underlying mechanism of these associations is unknown; this study may promote research concerning ET strategies and promote comprehensive consultations and recommendations for patients.

STUDY FUNDING/COMPETING INTEREST(S)
This work was supported by the Natural Science Foundation of China (Grant No.81571409), Science and Technology Research Project of Henan (Grant No. 172102310009) and Medical Science and Technology Research Project of Henan (Grant No. 201701005). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER
N/A