Effect of Long-Term Embryo Cryopreservation on Subsequent Frozen Embryo Transfer Outcomes: A Retrospective Cohort...

The duration of cryopreservation of embryos and its effect on the subsequent pregnancy outcomes, when they have been frozen for a longer duration remains a matter of concern. There is a continuous debate among studies comparing different durations of embryo cryopreservation as the results are contradictory.

This study aims to find out if long-term cryopreservation of embryos has any effect on pregnancy and perinatal outcomes.

:Retrospective cohort study was conducted in the department of reproductive medicine and surgery in a university-level teaching hospital.

The study included women who underwent frozen embryo transfer (FET) from autologous in vitro fertilisation between January 2012 and December 2020 with the duration of cryopreservation of more than 5 years as one group and 3-5 years as another group. Pregnancy and perinatal outcomes were analysed.

Regression analysis was performed using logistic regression by entering clinically important variables associated with pregnancy outcome, and the results were expressed as odds ratio with a 95% confidence interval (CI). All statistical analysis was performed with SPSS (version 21.0, IBM, USA).

A total of 1680 FET cycles were carried out during the study period. Among these, 75 cycles with a duration of 3-5 years and 20 cycles with a duration of more than 5 years were included. Live birth rate (LBR) was 40.8% in the 3-5 years group and 35% in the more than 5 years group. After adjusting for important confounders, the LBR has no significant association in the more than 5 years group (adjusted odds ratio 1.07; 95% CI 0.34-3.32; P = 0.913) compared to the 3-5 years group.

The duration of cryopreservation of embryos has no statistically significant effect on the pregnancy and perinatal outcomes.