Human embryo vitrification is safe – but has significant limitations, according to an analysis published today.
Researchers from the Shanghai Ninth People’s Hospital in China followed the outcomes for 24,698 patients who had vitrified embryos transferred between January 2011 and December 2017.
Patients who had vitrified embryos stored for up to three months were compared with patients whose embryos were stored for three to six months, or for six to 12 months, or for 12 to 24 months.
The implantation success rate was 40% in the first group, falling steadily to 26% in the fourth group. Pregnancy was 56% in the first group and dropped to 26% in the fourth group. For live births, the rate was 47% in the first group, down to 26% in the fourth group.
Miscarriages and ectopic pregnancies increased with longer storage time, but only slightly, and there was no sign of an impact on the outcomes for the babies.
The research is published today (24 June) in Human Reproduction.
Lead researcher, Dr Qianqian Zhu, said: “Our results suggest that clinicians should consider the effect of storage duration before making decisions about the numbers of embryos to freeze and store.
“This is especially important for cancer patients, who may have their ovaries destroyed by cancer therapies and who have to delay fertility treatment until they have recovered from their disease.”
Co-author Professor Qifeng Lyu added: “Our study suggests that although the storage time of vitrified embryos negatively affected pregnancy outcomes, including clinical pregnancy and live birth rates, it did not affect neonatal outcomes. Our study demonstrated the safety of using long-stored embryos after vitrification on neonatal health.”
Li, J. et al. The effect of storage time after vitrification on pregnancy and neonatal outcomes among 24,698 patients following the first embryo transfer cycles. Human Reproduction 24 June 2020 doi: 10.1093/humrep/deaa136
https://academic.oup.com/humrep/article-lookup/doi/10.1093/humrep/deaa136
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