Childhood growth of term singletons born after frozen compared with fresh embryo transfer

RESEARCH QUESTION

Is the growth of term singletons born after frozen embryo transfer (FET) comparable to those born after fresh embryo transfer and natural conception up to 5 years of age?

DESIGN

Observational cohort study in an academic medical centre and municipal child health clinics with repeated measurements carried out by medical professionals. Term singletons born after FET (n = 110) and fresh embryo transfer (n = 181) and their matched natural conception controls (n = 543) born in Oulu, Northern Finland, were included. Mean weights, lengths, heights and head circumferences at the ages of 4, 8 and 18 months and 3 and 5 years were compared. At 3 and 5 years, body mass indices were compared.

RESULTS

Childhood growth did not differ between term singletons born after FET, fresh embryo transfer and natural conception, correcting for exact age at measurement and adjusting for maternal body mass index and paternal height.

CONCLUSIONS

Similar growth between children born after FET, fresh embryo transfer and natural conception offers reassurance of the safety and feasibility of the steadily increasing use of embryo cryopreservation in assisted reproduction.

P–791 Comparison of the live birth rate after single embryo transfer in fresh versus frozen cycle: no evidence to support routine freeze-all strategy

Study question

Is the treatment outcome compromised after superovulation for fresh IVF/ICSI in comparison to frozen cycle with spontaneous ovulation and luteal support with progesterone?

Summary answer

Live birth rate (LBR) is dependent on embryo quality both in the fresh and frozen cycles with no sign of harmful effect of the superovulation.

What is known already

Freeze-all strategy has been advocated in recent years based on the assumption that luteal phase after superovulation is not optimal for embryo implantation. The effects of variable hormonal treatments, given in association with ART, on the endometrium, are still largely unknown. Therefore, more data is needed in order to optimize the treatment policies.

Study design, size, duration

This is an observational retrospective single-center cohort study. Data were collected from Oulu University Hospital’s ART-database including a total of 5647 single embryo transfer cycles from years 1995–2020. Patients stimulated with long agonist protocol for IVF/ICSI and day 2–3 transfer were included. Frozen embryo transfer was performed in a natural cycle with an ovulation test used for timing of transfer. Luteal support with progesterone was given for two weeks in all cycles.

Participants/materials, setting, methods

There were 3053 IVF/ICSI fresh cycles (2237 top and 816 N-top) and 2594 frozen cycles (806 top and 1788 N-top). The main outcome measure was LBR compared between fresh and frozen cycles when either a top or a N-top embryo was transferred. As a secondary outcome, clinical pregnancy rate was investigated. Data on the age and body mass index (BMI) of the patients was available. Student’s T-test was used to compare continuous variables.

Main results and the role of chance

The groups did not differ regarding the age and BMI of the patients. After the transfer of a top quality embryo the clinical pregnancy rate (35.4 vs. 30.8%; p < 0.05) and LBR (29.4 vs. 25.5%; p not significant) was slightly higher in the fresh cycle. After the transfer of a N-top quality embryo the clinical pregnancy rate (19.9 vs. 19.4%) and LBR (15.9 vs. 15.4%) were similar both in the fresh and frozen cycles.

Limitations, reasons for caution

This study only represents cleavage stage embryo transfers, and all FETs were performed in a natural cycle. In a retrospective study there may also be residual confounding that could not be excluded.

Wider implications of the findings: This study provides further evidence that treatment outcome regarding LBR is not affected by superovulation therapy. Hence, the use of freeze-all strategy is warranted only in cases with a risk of ovarian hyperstimulation syndrome.

Trial registration number

Not applicable