Pregnancy and neonatal outcomes of blastocysts without blastocoele re-expansion in FET patients: are they of clinical value?

OBJECTIVE

To study if the transfer of warmed blastocysts without blastocoele re-expansion is effective and safe.

METHODS

Three thousand one hundred ninety-six frozen-thawed single blastocyst transfer cycles were conducted. The embryos were categorized into two groups based on the occurrence of blastocoele re-expansion following a post-warming culture period of 3-4 h, including non-re-expanded blastocyst transfer group (n = 431) and re-expanded blastocyst transfer group (n = 2765). Propensity score matching was utilized to mitigate potential confounding factors across groups. The pregnancy and neonatal outcomes were analyzed and compared between the two groups before and after the implementation of propensity score matching.

RESULTS

The rates of biochemical pregnancy, clinical pregnancy, intrauterine implantation, and live birth were significantly lower in the group that received a single frozen-thawed blastocyst without blastocoele re-expansion transfer, in comparison to the re-expanded blastocyst transfer group (before matching: 29.5% versus 60.7%, 21.6% versus 51.9%, 22.3% versus 52.0%, and 16.9% versus 41.6%, respectively, all P < 0.01). However, upon evaluating the pregnancy outcomes, no statistically significant differences were observed in the rates of ectopic pregnancy, miscarriage, multiple gestation, multiple births, and gestational age (P > 0.05) between the two groups. Furthermore, no significant differences were observed in neonatal outcomes, including live born infants, birth weight, delivery, and birth defects. Additionally, similar findings were also noted in the two matched cohorts after propensity score matching.

CONCLUSION

Warmed blastocysts that do not exhibit blastocoele re-expansion following a 3-4-h culture may be considered for transfer rather than being discarded in frozen-thawed embryo transfer (FET) cycles, resulting in acceptable clinical outcomes.