The benefits of frozen embryo transfer
Modern lifestyle and innovative vitrification techniques have changed the world’s perspective on Medically Assisted Reproduction.
HFEA (Human Fertilization & Embryology Authority, UK) recently published <<Fertility treatment 2021 >> with data from all reproductive centers across UK.
Reviewing the publication it is worth mentioned that:
- Average IVF pregnancy rates using fresh embryo transfers for patients aged 18-34 were 41% per embryo transferred (PET), compared to 6% for patients aged 43-50 when using their own eggs in 2021 (figure1)
- Preliminary average IVF birth rates using fresh embryo transfers for patients aged 18-34 were 33% per embryo transferred, compared to 4% for patients aged 43-50 when using their own eggs in 2021
- The average age of IVF patients increased; a trend shown and already published in 2010, that the majority of women where aged 37 and under.
- For patients aged 40-42 pregnancy rate per embryo transferred reached 16%, while for patients aged 43-50 pregnancy rate per embryo transferred are 6% in 2021.
- The average IVF pregnancy rate using frozen embryo transfers increased from around 7% in the 1990s to 36% in 2021
- When using frozen embryo transfer data, pregnancy and birth rates are largely dependent on the age of the patient at embryo freezing rather than age at embryo transfer.
Fertility treatment 2014-2016 (hfea.gov.uk)
Figure 11: IVF birth rates by age, 2016
In 2016, women under 35s were the only age group where fresh IVF had a notably higher birth rate PET than frozen. For the 38–39, 40–42 and 43–44 age groups, frozen cycles were around five percentage points more successful than fresh cycles.
Fertility treatment in 2010 trends and figures, HFEA
How does the live birth rate of frozen embryo transfers compare to that of fresh embryo transfers?
As noted above, fresh transfers tend to be more successful than frozen ones, with a higher overall pregnancy rate and higher overall live birth rate. Comparing live birth rates directly between fresh and frozen transfers (Figure 11) we see that while this trend is true for the youngest groups (where most of the cycles are performed), the trend is reversed in the older age groups.
Again, this may be because the embryos transferred in the frozen cycle were created using eggs collected some time ago, when the woman was herself younger.