Effects of different embryonic development days on clinical outcomes of freeze-thawed embryo transfer

To compare the clinical outcome of freeze-thawed embryo transfer at different embryonic development days in whole embryo freezing patients of different ages.

This was a retrospective study. Collected clinical data of 558 patients who underwent freeze-thawed embryo transfer at Reproductive Center of Baoding Maternal and Child Health Hospital from March 2019 to January 12, 2022. The enrolled patients were divided into two groups of 21~35 years old group(n=421) and 35~50 years old group(n=137) according to their ages. Then, three subgroups were established according to the development days of the freeze-thawed embryos under different age groups, D3 subgroup, D5 subgroup and D6 subgroup.

There were no significant differences in biochemical pregnancy rate, clinical pregnancy rate, multiple pregnancy rate, abortion rate, among the three groups in the 21~35 years old group. While significant difference was observed the highest embryo implantation rate in D5 subgroup(P<0.05). Meanwhile, in 35~50 years old group, the biochemical pregnancy rate in D5 subgroup was significantly higher than that in D3 and D6 subgroups(P<0.05). The clinical pregnancy rate of D5 subgroup was significantly higher than that of D6 subgroup(P<0.05), and the clinical pregnancy rate of D5 subgroup was higher than that of D3 subgroup(P>0.05). The embryo implantation rate in D5 subgroup was significantly higher than that in D3 and D6 subgroups(P<0.05).

Compared with D3 and D6 transfer strategies, D5-blastocyst transfer exhibits more satisfactory clinical outcomes, with the highest clinical pregnancy and embryo implantation rates.