A group of Chinese researchers Yuan Yuan, Qingyun Mai, Jiaxuan Ma, Mingfen Deng, Yanwen Xu, Guanglun Zhuang, Canguan Iun set themselves the task of finding out how long human embryos can be stored under conditions of cryonconservation (for an experimental period up to 12 years) and while remaining viable.
As a result of the experiment, a definite answer was obtained:
human embryos remain usable after prolonged storage in a cryobank.
In several cohort studies, neonatal cases with human embryos that have been cryopreserved for 5 years have been mentioned. Only a few reports have described the successful birth of children from human embryos after prolonged cryonconservation up to 12 years.
The retrospective observational study of the Chinese scientists in question included the observation of 20 patients (128 embryos) from March 2016 to April 2017.
Twenty patients were under observation who had at least one live birth during previous IVF / ICSI procedures and who had cryopreserved surplus of embryos. Data on recovery of frozen embryos, pregnancy and obstetric results were recorded.
The duration of embryo storage was 12.0–17.1 years, averaging 13.9 ± 1.73 years. A total of 115 embryos were thawed for transfer, with a survival rate of 74%. Sixty embryos were further cultured, resulting in 20 blastocysts with a blastocyst formation rate of 33%. 21 embryos at the cleavage stage and 13 blastocysts underwent a total of 12 and 11 cycles, respectively, resulting in one biochemical pregnancy, one miscarriage in the first trimester of pregnancy, two ectopic pregnancies, three singlets and one case of twins with clinical pregnancy, while the frequency the incidence of pregnancy was 25% (D3 ET) and 36% (blastocyst), 17% live birth (D3 ET) and 27% (blastocyst). Two out of four patients born alive developed gestational diabetes. One out of five live births was premature.
The sample was small due to the unique population of the study, and all embryos were slowly frozen. The fate of long-term cryopreserved embryos after freezing is still unclear.
The results obtained confirmed the possibility of using embryos after prolonged cryopreservation while maintaining fertile function.
This study was supported by grants from the China National Research and Development Program and the Guangzhou Science Program. None of the authors objected to the publication of the research results.
Based on Oxford Academic
