Endometriosis, endometrium, implantation and fallopian tube
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This retrospective cohort study found that transferring frozen blastocysts resulted in significantly higher pregnancy rates compared to transferring frozen cleavage stage embryos.
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Abstract
Study question: To compare the pregnancy rate in patients submitted to FET (Frozen Embryos Transfer) of cleavage stage embryos (Group 1), or at the blastocyst stage (Group 2). Summary answer: Our data showed that the transfer of frozen blastocysts has a better pregnancy rate than cleavage embryos. What is known already: The first birth of a baby arising from a cryopreserved embryo occurred in 1983. Since then, improvements in embryo cryopreservation have occurred. However since early 90 s a vitrification technique has also been developed to cryopreserve embryos in any stage of development. Study design, size, duration: Retrospective cohort study during 2012, with a total of 132 cycles. Participants/materials, setting, methods: In the group 1 the embryos had been frozen on the 2 nd , 3 rd or 4 th day after fertilization, while in the group 2 the embryos were frozen on 5 th or 6 th day at blastocyst stage. All embryos were cryopreserved by vitrification followed Kuwayama et al, 1998 protocol. The pregnancy rates were compared through the chi-square test (p , 0.05). Main results and the role of chance: The Group 1 consisted of 74 patients, which pregnancy and clinical pregnancy rate were 27.0% (20/74) and 21.6% (16/74), respectively. The Group 2 had 58 patients, and pregnancy and clinical pregnancy rate were 50.0% (29/58) and 43.1% (25/58) respectively. There was statistical difference between the groups (P 0.0107). The mean age were 34.8 and years old for groups 1 and 2 respectively. Limitations, reason for caution: The study was conducted during a short period of time. Wider implications of the findings: This result suggests that the transfer of embryos at the blastocyst stage would be the best choice for IVF clinics. Study funding/competing interest(s): There were no competing interests in this study.
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- last seen: 2026-06-10T17:14:06.276822+00:00
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