• Zabeena Pandian, Siladitya Bhattacharya, Ozkan Ozturk, Gamal Serour, and Allan Templeton.
• Obstetrics & Gynaecology, Aberdeen Maternity Hospital, Foresterhill, Aberdeen , UK, AB25 2ZD. ogy211@abdn.ac.uk
• Cochrane Db Syst Rev. 2009 Apr 15 (2): CD003416.

BackgroundMultiple embryo transfer during IVF has increased multiple pregnancy rates (MPR) causing maternal and perinatal morbidity. Elective single embryo transfer (SET) is now being considered as an effective means of reducing this iatrogenic complication.ObjectivesTo determine in couples undergoing IVF/ICSI (intra-cytoplasmic sperm injection) whether:(1) elective transfer of two embryos improves the probability of livebirth compared with:(a) elective single embryo transfer,(b) three embryo transfer (TET) or(c) four embryo transfer (FET).(2) elective transfer of three embryos improves the probability of livebirth compared with:(a) elective single embryo transfer, or(b) elective four embryo transfer.Search StrategyWe searched the Cochrane Menstrual Disorders and Subfertility Group's trials register (searched March 2008), the Cochrane Central Register of Controlled Trials (Cochrane Library, Issue 1, 2008), MEDLINE (1970 to 2008), EMBASE (1985 to 2008) and reference lists of articles. Relevant conference proceedings were hand-searched and researchers in the field contacted.Selection CriteriaRandomised controlled trials were included.Data Collection And AnalysisTwo reviewers independently assessed eligibility and quality of trials.Main ResultsFor the update in 2008 five trials compared DET with SET. DET versus TET and DET versus FET were evaluated in a single small trial each. The difference in cumulative livebirth rates (CLBR) after DET and those after SET followed by transfer of a single frozen thawed embryo (1FZET) was not statistically significant (OR 0.81, 95% CI 0.59 to 1.11; p=0.18). There was no statistically significant difference in CLBR after a single fresh cycle of DET versus two fresh cycles of SET (OR 1.23, 95% CI 0.56 to 2.69, p= 0.60 ). The live birth rate (LBR) per woman in a single fresh treatment was higher following DET than SET (OR 2.10, 95% CI 1.65 to 2.66, p<0.00001). The MPR was lower following SET (OR 0.04, 95% CI 0.01 to 0.11; p< 0.00001). The CLBR following two fresh cycles of DET versus two fresh cycles of TET (OR 0.77, 95%CI 0.22 to 2.65, p=0.67) and CLBR after three fresh cycles of DET versus three fresh cycles of TET showed no statistically significant differences (OR 0.77, 95% CI 0.24 to 2.52; p=0.67). There were no statistically significant differences between DET and TET in terms of LBR (OR 0.40, 95%CI 0.09 to 1.85; p=0.24) and MPR (OR 0.17, 95%CI 0.01 to 3.85; p= 0.27). DET led to lower LBR than FET but the difference was not statistically significant (OR 0.35, 95% CI 0.11 to 1.05; p = 0.06).Authors' ConclusionsIn a single fresh IVF cycle, SET is associated with a lower LBR than DET. However there is no significant difference in CLBR following SET+ 1FZET and the LBR following a single cycle of DET. MPR are lowered following SET compared with other transfer policies. There are insufficient data on the outcome of two versus three and four embryo transfer policies.

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