Medical Statistics Team, Section of Population Health, University of Aberdeen, Aberdeen AB25 2ZD, UK.
BMJ. 2010 Dec 21;341:c6945. doi: 10.1136/bmj.c6945.
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.
One stage meta-analysis of individual patient data.
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.
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).
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.
比较新鲜胚胎移植时选择性单胚胎移植与双胚胎移植对活产、多胎活产、流产、早产、足月单胎产和低出生体重的影响，以及对新鲜和冷冻胚胎移植后累计活产和多胎活产的影响。
个体患者数据的单阶段荟萃分析。
对 Medline、Embase 和 Cochrane 对照试验中央注册库（截至 2008 年）的英文和非英文文章进行系统评价。通过与临床专家联系和检索所有相关原始文章的参考文献，确定了其他研究。检索词包括胚胎移植、随机对照试验、对照临床试验、单胚胎移植和双胚胎移植。
纳入了新鲜体外受精（IVF）或胞浆内单精子注射（ICSI）治疗中卵裂期（第 2 或 3 天）选择性单胚胎与双胚胎移植的临床有效性比较的研究。如果干预仅在预期移植胚胎的数量上有所不同，则纳入试验。仅涉及囊胚（第 5 天）转移的试验被排除在外。
共收到了纳入的八项符合条件的试验（n=1367）中每位患者的个体患者数据。分别有 683 名和 684 名妇女随机分配到单胚胎和双胚胎移植组，纳入了分析。两组的基线特征相似。新鲜 IVF 周期中单胚胎转移后的总活产率（181/683，27%）低于双胚胎转移（285/683，42%）（调整后的比值比 0.50，95%置信区间 0.39 至 0.63），多胎产率（3/181（2%）比 84/285（29%））（0.04，0.01 至 0.12）也较低。然而，单次冷冻胚胎移植后，累计活产率并未显著低于单次新鲜双胚胎移植后的活产率（132/350（38%）比 149/353（42%）（0.85，0.62 至 1.15），且多胎累积风险最小（1/132（1%）比 47/149（32%））。选择性单胚胎转移后足月单胎分娩（即超过 37 周）的几率几乎是双胚胎转移后的五倍（4.93，2.98 至 8.18）。
与双胚胎移植相比，选择性单胚胎移植更有可能分娩足月单胎活产儿。尽管这种策略在新鲜 IVF 周期中的妊娠率低于双胚胎移植，但这一差异几乎可以通过单次冷冻胚胎移植周期完全弥补。选择性单胚胎移植后的多胎妊娠率与自然妊娠观察到的妊娠率相当。
