Mathilde Bourdon1,2, Khaled Pocate-Cheriet3,4, Astri Finet de Bantel5, Veronika Grzegorczyk-Martin5, Aureli Amar Hoffet6, Elisangela Arbo7, Marine Poulain8,9, Pietro Santulli1,2. 1. Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique-Hôpitaux de Paris, Hôpital Universitaire Paris Centre, Centre Hospitalier Universitaire Cochin, Service de Gynécologie-Obstétrique II et de Médecine de la Reproduction, Université Paris Descartes, 53 Avenue de l'Observatoire, 75014 Paris, France. 2. Département Stress Oxydant, Prolifération Cellulaire et Inflammation, Institut Cochin, INSERM (Institut national de la santé et de la recherche médicale) U1016, Université Paris Descartes, Sorbonne Paris Cité, 22 Rue Mechain, 75014 Paris, France. 3. Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique-Hôpitaux de Paris, Hôpital Universitaire Paris Centre, Centre Hospitalier Universitaire Cochin, Service d'Histologie-Embryologie-Biologie de la Reproduction, Université Paris Descartes, 53 Avenue de l'Observatoire, 75014 Paris, France. 4. Département Génomique, Epigénétique et Physiopathologie de la Reproduction, Institut Cochin, INSERM (Institut national de la santé et de la recherche médicale) U1016, CNRS UMR8104, Université Paris Descartes, Sorbonne Paris Cité, 22 Rue Mechain, 75014 Paris, France. 5. Médecine de la Reproduction, Clinique Mathilde, 7 Boulevard de l'Europe, 76100 Rouen, France. 6. Hôpital Saint Joseph, 26 Boulevard de Louvain, 13008 Marseille, France. 7. Gedeon Richter France, 103 Boulevard Haussmann 75008 Paris, France. 8. Unité de Biologie de la Reproduction, Service de Gynécologie Obstétrique et Médecine de la Reproduction, Hôpital Foch, 40 Rue Worth, 92151 Suresnes, France. 9. Gametes-Gestation-Implantation (EA 7404), Université Versailles Saint Quentin, 2 Avenue de la Source de la Bièvre 78180 Montigny-le-Bretonneux, France.
Abstract
STUDY QUESTION: Is there a difference in clinical pregnancy and live birth rates (LBRs) between blastocysts developing on Day 5 (D5) and blastocysts developing on Day 6 (D6) following fresh and frozen transfers? SUMMARY ANSWER: D5 blastocyst transfers (BTs) present higher clinical pregnancy and LBRs than D6 in both fresh and frozen transfers. WHAT IS KNOWN ALREADY: BT is increasingly popular in assisted reproductive technology (ART) centers today. To our knowledge, no meta-analysis has focused on clinical outcomes in both fresh and frozen BT. Concerning frozen blastocysts, one meta-analysis in 2010 found no significant difference in pregnancy outcomes between D5 and D6 BT. Since then, ART practices have evolved particularly with the wide use of vitrification, and more articles comparing D5 and D6 BT cycles have been published and described conflicting results. STUDY DESIGN, SIZE, DURATION: Systematic review and meta-analysis of published controlled studies. Searches were conducted from 2005 to February 2018 on MEDLINE and Cochrane Library and from 2005 to May 2017 on EMBASE, Eudract and clinicaltrials.gov, using the following search terms: blastocyst, Day 5, Day 6, pregnancy, implantation, live birth and embryo transfer (ET). PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 47 full-text articles were preselected from 808 references, based on title and abstract and assessed utilizing the Newcastle-Ottowa Quality Assessment Scales. Study selection and data extraction were carried out by two independent reviewers according to Cochrane methods. Random-effect meta-analysis was performed on all data (overall analysis) followed by subgroup analysis (fresh, vitrified/warmed, slow frozen/thawed). MAIN RESULTS AND THE ROLE OF CHANCE: Data from 29 relevant articles were extracted and integrated in the meta-analysis. Meta-analysis of the 23 studies that reported clinical pregnancy rate (CPR) as an outcome, including overall fresh and/or frozen ET cycles, showed a significantly higher CPR following D5 ET compared with D6 ET (risk ratio (RR) = 1.27, 95% CI: 1.15-1.39, P < 0.001). For CPR, calculated subgroup RRs were 2.38 (95% CI: 1.74-3.24, P < 0.001) for fresh BT; 1.27 (95% CI: 1.16-1.39, P < 0.001) for vitrified/warmed BT; and 1.15 (95% CI: 0.93-1.41, P = 0.20) for slow frozen/thawed BT. LBR was also significantly higher after D5 BT (overall RR = 1.50 (95% CI: 1.32-1.69), P < 0.001). The LBR calculated RRs for subgroups were 1.74 (95% CI: 1.37-2.20, P < 0.001) for fresh BT; 1.38 (95% CI: 1.23-1.56, P < 0.001) for vitrified/warmed BT; and 1.44 (95% CI: 0.70-2.96, P = 0.32) for slow frozen/thawed BT. Sensitivity analysis led to similar results and conclusions: CPR and LBR were significantly higher following D5 compared to D6 BT. LIMITATIONS, REASONS FOR CAUTION: The validity of meta-analysis results depends mainly on the quality and the number of the published studies available. Indeed, this meta-analysis included no randomized controlled trial (RCT). Slow frozen/thawed subgroups showed substantial heterogeneity. WIDER IMPLICATIONS OF THE FINDINGS: In regards to the results of this original meta-analysis, ART practitioners should preferably transfer D5 rather than D6 blastocysts in both fresh and frozen cycles. Further RCTs are needed to address the question of whether D6 embryos should be transferred in a fresh or a frozen cycle. STUDY FUNDING/COMPETING INTEREST(S): This work was sponsored by an unrestricted grant from GEDEON RICHTER France. The authors have no competing interests to declare. REGISTRATION NUMBER: CRD42018080151.
STUDY QUESTION: Is there a difference in clinical pregnancy and live birth rates (LBRs) between blastocysts developing on Day 5 (D5) and blastocysts developing on Day 6 (D6) following fresh and frozen transfers? SUMMARY ANSWER: D5 blastocyst transfers (BTs) present higher clinical pregnancy and LBRs than D6 in both fresh and frozen transfers. WHAT IS KNOWN ALREADY: BT is increasingly popular in assisted reproductive technology (ART) centers today. To our knowledge, no meta-analysis has focused on clinical outcomes in both fresh and frozen BT. Concerning frozen blastocysts, one meta-analysis in 2010 found no significant difference in pregnancy outcomes between D5 and D6 BT. Since then, ART practices have evolved particularly with the wide use of vitrification, and more articles comparing D5 and D6 BT cycles have been published and described conflicting results. STUDY DESIGN, SIZE, DURATION: Systematic review and meta-analysis of published controlled studies. Searches were conducted from 2005 to February 2018 on MEDLINE and Cochrane Library and from 2005 to May 2017 on EMBASE, Eudract and clinicaltrials.gov, using the following search terms: blastocyst, Day 5, Day 6, pregnancy, implantation, live birth and embryo transfer (ET). PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 47 full-text articles were preselected from 808 references, based on title and abstract and assessed utilizing the Newcastle-Ottowa Quality Assessment Scales. Study selection and data extraction were carried out by two independent reviewers according to Cochrane methods. Random-effect meta-analysis was performed on all data (overall analysis) followed by subgroup analysis (fresh, vitrified/warmed, slow frozen/thawed). MAIN RESULTS AND THE ROLE OF CHANCE: Data from 29 relevant articles were extracted and integrated in the meta-analysis. Meta-analysis of the 23 studies that reported clinical pregnancy rate (CPR) as an outcome, including overall fresh and/or frozen ET cycles, showed a significantly higher CPR following D5 ET compared with D6 ET (risk ratio (RR) = 1.27, 95% CI: 1.15-1.39, P < 0.001). For CPR, calculated subgroup RRs were 2.38 (95% CI: 1.74-3.24, P < 0.001) for fresh BT; 1.27 (95% CI: 1.16-1.39, P < 0.001) for vitrified/warmed BT; and 1.15 (95% CI: 0.93-1.41, P = 0.20) for slow frozen/thawed BT. LBR was also significantly higher after D5 BT (overall RR = 1.50 (95% CI: 1.32-1.69), P < 0.001). The LBR calculated RRs for subgroups were 1.74 (95% CI: 1.37-2.20, P < 0.001) for fresh BT; 1.38 (95% CI: 1.23-1.56, P < 0.001) for vitrified/warmed BT; and 1.44 (95% CI: 0.70-2.96, P = 0.32) for slow frozen/thawed BT. Sensitivity analysis led to similar results and conclusions: CPR and LBR were significantly higher following D5 compared to D6 BT. LIMITATIONS, REASONS FOR CAUTION: The validity of meta-analysis results depends mainly on the quality and the number of the published studies available. Indeed, this meta-analysis included no randomized controlled trial (RCT). Slow frozen/thawed subgroups showed substantial heterogeneity. WIDER IMPLICATIONS OF THE FINDINGS: In regards to the results of this original meta-analysis, ART practitioners should preferably transfer D5 rather than D6 blastocysts in both fresh and frozen cycles. Further RCTs are needed to address the question of whether D6 embryos should be transferred in a fresh or a frozen cycle. STUDY FUNDING/COMPETING INTEREST(S): This work was sponsored by an unrestricted grant from GEDEON RICHTER France. The authors have no competing interests to declare. REGISTRATION NUMBER: CRD42018080151.
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