Transfer of human frozen-thawed embryos with further cleavage during culture increases pregnancy rates

AIM: To compare the pregnancy rate following transfer of frozen-thawed embryos with or without overnight culture after thawing. SETTINGS AND DESIGN: This is a retrospective analysis of frozen-thawed embryo transfer (FET) cycles performed between January 2006 and December 2008. MATERIALS AND METHODS: Out of 518 thaw cycles, 504 resulted in embryo transfers (ETs). Of the total FET cycles, 415 were performed after an overnight culture of embryos (group A); and in 89 cycles, ET was performed within 2 hours of embryo thawing (group B). STATISTICAL ANALYSIS: The data were statistically analyzed using chi-square test. RESULTS: We observed that with FET, women ≤30 years of age had a significantly higher (P=0.003) pregnancy rate (PR=28.9%) as compared to women >30 years of age (17.5%). A significantly higher (P<0.001**) pregnancy rate was also observed in women receiving 3 frozen-thawed embryos (29%) as compared to those who received less than 3 embryos (10.7%). The difference in PR between group A (PR=24.3%) and group B (PR=20.3%) was not statistically significant. However, within group A, ET with cleaved embryos showed significantly (P≤0.01) higher pregnancy rate compared to the uncleaved embryos, depending on the number of cleaved embryos transferred. CONCLUSION: No significant difference was noticed between FETs made with transfer of embryos with overnight culture and those without culture. However, within the cultured group, transfer of embryos cleaved during overnight culture gave significantly higher PR than transfers without any cleavage.