• Evangelos G Papanikolaou, Efstratios M Kolibianakis, Herman Tournaye, Christos A Venetis, Human Fatemi, Basil Tarlatzis, and Paul Devroey.
• Centre for Reproductive Medicine, University Hospital, Vrije Univestiteit Brussel (Free University of Brussels), Laarbeeklaaan 101, B-1090 Brussels, Belgium. evangelos.papanikolaou@vub.ac.be /
• Hum. Reprod. 2008 Jan 1; 23 (1): 91-9.

BackgroundBoth cleavage-stage and blastocyst-stage embryo transfer policies have advantages and drawbacks. The number of embryos transferred, however, is a crucial parameter that needs to be considered before attempting any comparison.MethodsAn extensive literature search yielded initially 282 studies from which 8 randomized controlled trials met the inclusion criteria: (i) truly randomized design (ii) policy to transfer equal number of embryos in both the cleavage-stage and the blastocyst-stage groups and (iii) published as full text in a peer-review journal. Primary outcome was the live birth rate and secondary outcomes were clinical pregnancy rate, multiple pregnancy rate, cancellation rate and cryopreservation rate.ResultsA total of 1654 patients were reviewed. Live birth rate per randomized patient was significantly higher (n = 6 studies) in patients who had a blastocyst-stage transfer as compared to patients with cleavage-stage embryo transfer [odds ratio (OR): 1.39, 95% confidence interval (CI): 1.10-1.76; P = 0.005]. Clinical pregnancy rate (OR: 1.27, 95% CI: 1.03-1.55; P = 0.02) and cancellation rate per patient randomized (OR: 2.21, 95% CI: 1.47-3.32; P = 0.0001) were significantly higher in patients with a blastocyst-stage embryo transfer as compared to patients in whom a cleavage-stage embryo transfer was performed. The cryopreservation rate was significantly higher in the cleavage-stage group (OR: 0.28, 95% CI: 0.14-0.55; P = 0.0002).ConclusionsThe best available evidence suggests that the probability of live birth after fresh IVF is significantly higher after blastocyst-stage embryo transfer as compared to cleavage-stage embryo transfer when equal number of embryos are transferred in the two groups compared.

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