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Meta-Analysis
. 2010 Dec 21:341:c6945.
doi: 10.1136/bmj.c6945.

Clinical effectiveness of elective single versus double embryo transfer: meta-analysis of individual patient data from randomised trials

D J McLernon  1 , K Harrild, C Bergh, M J Davies, D de Neubourg, J C M Dumoulin, J Gerris, J A M Kremer, H Martikainen, B W Mol, R J Norman, A Thurin-Kjellberg, A Tiitinen, A P A van Montfoort, A M van Peperstraten, E Van Royen, S Bhattacharya
Affiliations
Meta-Analysis

Clinical effectiveness of elective single versus double embryo transfer: meta-analysis of individual patient data from randomised trials

D J McLernon et al. BMJ. .

Abstract

Objective: To compare the effectiveness of elective single embryo transfer versus double embryo transfer on the outcomes of live birth, multiple live birth, miscarriage, preterm birth, term singleton birth, and low birth weight after fresh embryo transfer, and on the outcomes of cumulative live birth and multiple live birth after fresh and frozen embryo transfers.

Design: One stage meta-analysis of individual patient data.

Data sources: A systematic review of English and non-English articles from Medline, Embase, and the Cochrane Central Register of Controlled Trials (up to 2008). Additional studies were identified by contact with clinical experts and searches of bibliographies of all relevant primary articles. Search terms included embryo transfer, randomised controlled trial, controlled clinical trial, single embryo transfer, and double embryo transfer. Review methods Comparisons of the clinical effectiveness of cleavage stage (day 2 or 3) elective single versus double embryo transfer after fresh or frozen in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) treatments were included. Trials were included if the intervention differed only in terms of the intended number of embryos to be transferred. Trials that involved only blastocyst (day five) transfers were excluded.

Results: Individual patient data were received for every patient recruited to all eight eligible trials (n=1367). A total of 683 and 684 women randomised to the single and double embryo transfer arms, respectively, were included in the analysis. Baseline characteristics in the two groups were comparable. The overall live birth rate in a fresh IVF cycle was lower after single (181/683, 27%) than double embryo transfer (285/683, 42%) (adjusted odds ratio 0.50, 95% confidence interval 0.39 to 0.63), as was the multiple birth rate (3/181 (2%) v 84/285 (29%)) (0.04, 0.01 to 0.12). An additional frozen single embryo transfer, however, resulted in a cumulative live birth rate not significantly lower than the rate after one fresh double embryo transfer (132/350 (38%) v 149/353 (42%) (0.85, 0.62 to 1.15), with a minimal cumulative risk of multiple birth (1/132 (1%) v 47/149 (32%)). The odds of a term singleton birth (that is, over 37 weeks) after elective single embryo transfer was almost five times higher than the odds after double embryo transfer (4.93, 2.98 to 8.18).

Conclusions: Elective single embryo transfer results in a higher chance of delivering a term singleton live birth compared with double embryo transfer. Although this strategy yields a lower pregnancy rate than a double embryo transfer in a fresh IVF cycle, this difference is almost completely overcome by an additional frozen single embryo transfer cycle. The multiple pregnancy rate after elective single embryo transfer is comparable with that observed in spontaneous pregnancies.

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Conflict of interest statement

Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work apart from the funding from the Wellcome Trust (mentioned above); MJD received a research grant from the National Health and Medical Research Council, DdeN is secretary of the VWRG (Reproductive Medicine subgroup of the Flemish Gynaecological society) and received travel and accommodation sponsored by Schering-Plough for the 6th world congress on ovulation induction; with the exception of DJM, KH, BWM, and AMvanP, all authors were involved in the conduct of the primary randomised trials included in this systematic review.

Figures

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Fig 1 Flow diagram of study selection
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Fig 2 Odds ratios of elective single embryo transfer v double embryo transfer for separate trials and pooled odds ratios for live births and multiple live births
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Fig 3 Odds ratios of live birth for elective single embryo transfer versus double embryo transfer by different subgroups
See this image and copyright information in PMC

Comment in

References

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