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Hum Reprod Update. 2014 May-Jun;20(3):439-48. doi: 10.1093/humupd/dmu001. Epub 2014 Jan 30.
Several studies have evaluated outcomes of singleton pregnancies after blastocyst versus cleavage stage embryo transfer. Higher incidences of preterm birth (PTB), very preterm birth (VPTB), low birthweight (LBW) and congenital malformations were identified in a few of them. The objective of our study was to systematically review and meta-analyze pregnancy and neonatal outcomes among singleton births following blastocyst versus cleavage stage embryo transfer. METHODS EMBASE, MEDLINE, EBM Reviews and bibliographies of included studies were searched from their inception until March 2013. Observational studies or clinical trials comparing blastocyst with cleavage stage embryo transfer and reporting on outcomes of PTB (<37 weeks), VPTB (<32 weeks), LBW (<2500 g), very low birthweight (VLBW) (<1500 g) and/or congenital anomalies in singleton neonates were included. Data on the outcomes were extracted by two reviewers. Statistical heterogeneity among studies was evaluated by calculating I(2) values and χ(2) statistics. Meta-analyses were conducted to estimate the pooled unadjusted odds ratio (OR) and the adjusted OR (AOR) with a 95% confidence interval (CI) using the random effect model. RESULTS Six observational studies, of low to moderate risk of bias, were included in this review. There were significantly higher odds of PTB (four studies, 54 792 cleavage stage and 20 724 blastocyst stage births; AOR 1.32, 95% CI 1.19-1.46) and congenital anomalies (two studies, 22 068 cleavage stage and 4517 blastocyst stage births; AOR 1.29, 95% CI 1.03-1.62) among births after blastocyst transfer compared with cleavage stage transfer. There was no difference in the adjusted odds of VPTB (four studies, 54 792 cleavage stage and 20 724 blastocyst stage births; AOR 1.18, 95% CI 0.93-1.49), LBW (four studies, 54 109 cleavage stage and 20 392 blastocyst stage births; AOR 1.06, 95% CI 0.99-1.15) or VLBW (three studies, 22 088 cleavage stage and 5772 blastocyst stage births; AOR 1.01, 95% CI 0.73-1.38). CONCLUSIONS Risk of PTB in IVF singleton pregnancies is significantly higher following blastocyst transfer compared with cleavage stage transfer. Risk of congenital anomalies may also be higher but further studies are needed to confirm this finding and to identify reasons for such outcomes.
几项研究评估了囊胚期和卵裂期胚胎移植后单胎妊娠的结局。其中一些研究发现，早产（PTB）、极早产（VPTB）、低出生体重（LBW）和先天性畸形的发生率较高。我们的研究目的是系统地回顾和荟萃分析囊胚期和卵裂期胚胎移植后单胎出生的妊娠和新生儿结局。
从成立之初到 2013 年 3 月，检索了 EMBASE、MEDLINE、EBM 评价和纳入研究的参考文献。纳入了比较囊胚期和卵裂期胚胎移植并报告单胎新生儿早产（<37 周）、极早产（<32 周）、低出生体重（<2500g）、极低出生体重（<1500g）和/或先天性畸形结局的观察性研究或临床试验。两名评审员提取了结局数据。通过计算 I(2)值和 χ(2)统计量评估研究间的统计学异质性。使用随机效应模型，进行荟萃分析以估计未调整的合并优势比（OR）和调整后的 OR（AOR）及其 95%置信区间（CI）。
本综述纳入了 6 项低至中度偏倚风险的观察性研究。囊胚期转移后出生的 PTB（4 项研究，54792 例卵裂期和 20724 例囊胚期出生；AOR 1.32，95%CI 1.19-1.46）和先天性异常（2 项研究，22068 例卵裂期和 4517 例囊胚期出生；AOR 1.29，95%CI 1.03-1.62）的可能性明显较高。囊胚期转移与卵裂期转移相比，VPTB（4 项研究，54792 例卵裂期和 20724 例囊胚期出生；AOR 1.18，95%CI 0.93-1.49）、LBW（4 项研究，54109 例卵裂期和 20392 例囊胚期出生；AOR 1.06，95%CI 0.99-1.15）或 VLBW（3 项研究，22088 例卵裂期和 5772 例囊胚期出生；AOR 1.01，95%CI 0.73-1.38）的调整后的 odds 比值无差异。
与卵裂期相比，IVF 单胎妊娠囊胚期转移后的 PTB 风险显著增加。先天性异常的风险也可能更高，但需要进一步的研究来证实这一发现，并确定导致这些结果的原因。
