STUDY QUESTION: Do cumulative live birth rates differ between single cleavage-stage Day 3 transfer and single blastocyst-stage Day 5 transfer? SUMMARY ANSWER: Cumulative live birth rates after Day 3 and 5 transfers were similar in young patients when the vitrified embryo transfers were also taken into account. WHAT IS KNOWN ALREADY: Previous evidence has shown that the probability of live birth following IVF with a fresh embryo transfer is significantly higher after blastocyst-stage Day 5 transfer. However, because the introduction of vitrification has enhanced the survival of cryopreserved embryos and improved pregnancy rates, the optimal outcome measure for this comparison should now be cumulative live birth rates, as these include the eventual contribution of vitrified-warmed embryos. STUDY DESIGN, SIZE, DURATION: Our retrospective study included first IVF/ICSI cycles performed between January 2010 and December 2013 at a tertiary care centre. PARTICIPANTS/MATERIALS, SETTING, METHODS: All patients were scheduled for fresh single embryo transfer, either on Day 3 (n = 377) or on Day 5 (n = 623). Both IVF and ICSI cycles were included and the sperm used were either fresh or frozen partner ejaculates, or frozen donor ejaculates. The primary outcome was cumulative live birth (after 24 weeks) rate per started cycle, including the eventual contribution of vitrification until the birth of a first child. MAIN RESULTS AND THE ROLE OF CHANCE: Live birth rates per started cycle were significantly lower after transferring the fresh single cleavage-stage embryo, compared to a blastocyst (31.3% and 37.8%, respectively, P = 0.041). Furthermore, the number of embryo transfers necessary until the first live birth was significantly lower for blastocyst-stage embryos (P < 0.001). However, the cumulative live birth rates were 52.6% for cleavage-stage and 52.5% for blastocyst-stage transfers (P = 0.989). LIMITATIONS, REASONS FOR CAUTION: The extrapolation of the results is limited by the retrospective nature of the study. Furthermore, the analysis was restricted to patients under 36 years of age undergoing their first treatment cycle. WIDER IMPLICATIONS OF THE FINDINGS: These results deserve further clinical consideration in terms of time and cost efficiency. A subsequent analysis of the neonatal outcomes is necessary to confirm the safety of treatment cycles using extended culture. STUDY FUNDING/COMPETING INTERESTS: No external funding was received and there are no conflicts of interest to declare.
STUDY QUESTION: Do cumulative live birth rates differ between single cleavage-stage Day 3 transfer and single blastocyst-stage Day 5 transfer? SUMMARY ANSWER: Cumulative live birth rates after Day 3 and 5 transfers were similar in young patients when the vitrified embryo transfers were also taken into account. WHAT IS KNOWN ALREADY: Previous evidence has shown that the probability of live birth following IVF with a fresh embryo transfer is significantly higher after blastocyst-stage Day 5 transfer. However, because the introduction of vitrification has enhanced the survival of cryopreserved embryos and improved pregnancy rates, the optimal outcome measure for this comparison should now be cumulative live birth rates, as these include the eventual contribution of vitrified-warmed embryos. STUDY DESIGN, SIZE, DURATION: Our retrospective study included first IVF/ICSI cycles performed between January 2010 and December 2013 at a tertiary care centre. PARTICIPANTS/MATERIALS, SETTING, METHODS: All patients were scheduled for fresh single embryo transfer, either on Day 3 (n = 377) or on Day 5 (n = 623). Both IVF and ICSI cycles were included and the sperm used were either fresh or frozen partner ejaculates, or frozen donor ejaculates. The primary outcome was cumulative live birth (after 24 weeks) rate per started cycle, including the eventual contribution of vitrification until the birth of a first child. MAIN RESULTS AND THE ROLE OF CHANCE: Live birth rates per started cycle were significantly lower after transferring the fresh single cleavage-stage embryo, compared to a blastocyst (31.3% and 37.8%, respectively, P = 0.041). Furthermore, the number of embryo transfers necessary until the first live birth was significantly lower for blastocyst-stage embryos (P < 0.001). However, the cumulative live birth rates were 52.6% for cleavage-stage and 52.5% for blastocyst-stage transfers (P = 0.989). LIMITATIONS, REASONS FOR CAUTION: The extrapolation of the results is limited by the retrospective nature of the study. Furthermore, the analysis was restricted to patients under 36 years of age undergoing their first treatment cycle. WIDER IMPLICATIONS OF THE FINDINGS: These results deserve further clinical consideration in terms of time and cost efficiency. A subsequent analysis of the neonatal outcomes is necessary to confirm the safety of treatment cycles using extended culture. STUDY FUNDING/COMPETING INTERESTS: No external funding was received and there are no conflicts of interest to declare.