卵裂期胚胎质量对单囊胚移植结局的影响

目的研究辅助生殖技术体外培养第3天胚胎质量对所形成的囊胚临床结局的影响。方法回顾性分析本中心行单囊胚移植的483个复苏周期共432个病人的资料,根据所移植囊胚在第3天卵裂期胚胎的细胞数和碎片量进行分组,分析细胞数量和碎片量对囊胚移植临床妊娠率、流产率的影响。根据第3天细胞数分成≤6细胞组、7~9细胞组和≥10细胞组3组;根据细胞碎片量分成≤2级组和≥3级组。结果碎片量≤2级组和≥3级组在临床妊娠率(57.14%vs.58.65%)、流产率(13.50%vs.16.67%)方面均无统计学差异(P0.05)。≤6细胞组、7~9细胞组和≥10细胞组的临床妊娠率分别为49.30%、60.24%、52.5%;流产率为31.43%、11.5%、14.29%,各组间临床妊娠率无统计学差异(P0.05),≤6细胞组的流产率明显高于7~9细胞组(P0.05)。≤6细胞组优质囊胚的流产率(28%)仍明显高于7~9细胞组(P0.05)。结论经囊胚培养形成的囊胚的临床妊娠率和流产率与第3天胚胎碎片的多少关系不大;第3天6细胞以下胚胎形成的囊胚质量较差,即使形成优质囊胚其发生流产的风险也较高。     

冷冻胚胎复苏移植中子宫内膜最佳容受时间的研究

目的 分析在冷冻胚胎复苏移植过程中，各种内膜准备的方案中的内膜转化后不同转化时间移植对妊娠率的影响。方法 回顾性分析2020年2至12月在广西壮族自治区生殖医院行冷冻囊胚复苏移植的1147周期，分析不同的内膜准备方案中不同的转化时间移植胚胎的妊娠率。结果 在激素替代周期中，内膜转化第5天移植的临床妊娠率为57.75%，内膜转化第6天移植的临床妊娠率为51.22%，两者妊娠率差异无统计学意义（P=0.413）。在自然周期自然排卵中，卵泡排卵第4天移植的临床妊娠率为42.86%，胚胎种植率为28.57%，排卵第5天移植临床妊娠率为62.04%，胚胎种植率为46.99%，排卵第6天移植临床妊娠率为64.71%，胚胎种植率为45.16%，排卵第7天移植无1例妊娠，四组的临床妊娠率总体差异无统计学意义（P=0.065），排卵第7天移植的胚胎种植率分别与排卵第5天移植和排卵第6天移植的胚胎种植率比较，差异均有统计学意义（P=0.038,P=0.033）。在自然周期注射HCG第5天移植的临床妊娠率为62.16%，注射HCG第6天移植的临床妊娠率为57.29%，注射HCG第7天移植临床妊娠率为54.5...     

体外受精中移植胚胎数目与临床妊娠结局的关系

目的探讨移植胚胎数目对临床妊娠结局的影响。方法根据移植胚胎数目的不同分为三组：1组为单胚胎移植组,2组为移植2个胚胎组,3组为移植3个胚胎组。分析三组患者移植的胚胎情况及移植后的临床妊娠结局。结果移植1个胚胎的妊娠率（20.7%）明显低于其它组（P〈0.05）,且流产率高（29.4%）,移植2个胚胎的妊娠率及种植率与移植3个胚胎的相似,但移植2个胚胎的流产率和多胎率明显低于移植3个组（P〈0.05）。结论单胚胎移植可以降低多胎率,但妊娠率偏低,移植2个胚胎可以获得较高的妊娠率并且可以降低多胎率的发生。     

早期卵裂作为胚胎质量预测指标对体外授精结局的影响

目的探讨早期卵裂是否可作为评估胚胎质量、胚胎种植率、临床妊娠率的预测指标。方法对2006年1月～2006年12月的471对夫妇，480个周期随机分A组和B组（对照组）。A组：262个周期，即从授精25～27h后观察2PN受精卵是否出现早期卵裂，同时第二天、第三天观察胚胎质量并进行分级；B组：218个周期，第二天、第三天观察胚胎质量并进行分级，但授精25—27h后不观察2PN受精卵是否出现卵裂。同时根据移植胚胎中含有出现早期卵裂的个数分为四组A，（三个移植胚胎均出现早期卵裂），A2（移植胚胎含两个出现早期卵裂），A1（移植胚胎一个出现早期卵裂），A0（移植胚胎无出现早期卵裂）。比较四组胚胎种植率。结果A组种植率和临床妊娠率均高于未观察早期卵裂B组，但统计学分析无显著意义；A3、A2、A1、A0组间胚胎种植率分别为30．9％、26．1％、21．2％、11．2％，有显著性差异（P〈0．001）。结论（1）第2，3天胚胎形态学分级依然可作为评定胚胎质量的参数。（2）早期卵裂是可作为预测高种植率胚胎的指标之一。     

冷冻胚胎复苏后胚胎继续发育情况与临床结局的关系

目的探讨冷冻胚胎复苏后胚胎继续发育情况与临床妊娠率、种植率、流产率和多胎率的关系。方法采用玻璃化方法冷冻保存第三天胚胎,胚胎复苏后继续培养1d,根据胚胎继续发育情况分为两组：第一组,至少有一个胚胎发育到致密期;第二组,没有胚胎发育到致密期。结果共分析了2011年1月到2012年5月213例复苏移植周期,第一组117个周期,平均移植胚胎2.71枚,临床妊娠率54.70%,种植率28.08%,流产率14.06%,多胎率32.81%。第二组96个周期,平均移植胚胎2.66枚,临床妊娠率40.63%,种植率17.25%,流产率30.77%,多胎率12.82%。两组种植率、流产率和多胎率比较,P〈0.05,均具有统计学差异。结论冷冻胚胎复苏后继续发育情况是胚胎质量的重要指标,与临床结局有密切关系。     

胚胎移植与囊胚移植的临床结局分析

背景：国内关于卵裂期胚胎移植与囊胚移植的临床比较与分析大样本报道较少见。 目的：比较第2,3天卵裂期胚胎移植与第5天囊胚移植的临床结局。 方法：选择2008-01/2009-12北京大学深圳医院生殖医学科行体外受精/卵胞浆内单精子显微注射共1612周期,比较第2,3天卵裂期胚胎移植与第5天囊胚移植的临床妊娠率、胚胎种植率、流产率、多胎率、出生婴儿性别比例等差异。 结果与结论：第2,3,5天移植组分别195,1 162,255周期,临床妊娠率分别为33.33%,38.04%,44.71%,种植率分别为21.37%,24.70%,31.96%;第5天移植组临床妊娠率和种植率均高于第2,3天移植组(P < 0.05);第2天移植组宫外孕发生率高于第3天移植组(P < 0.05)。3组流产、单卵双胎、多胎、早产及出生婴儿性别比例无差异。说明囊胚移植提高了临床妊娠率和种植率的同时,未增加流产、多胎、早产等风险,对男女性别比例的平衡无负面影响。     

冷冻方法对人卵裂期冷冻胚胎移植周期妊娠结局的影响

目的探讨慢速冷冻和玻璃化冷冻方法对人卵裂期冷冻胚胎移植周期妊娠结局的影响。方法回顾性分析2011年1月~2015年12月在北京大学第一医院进行卵裂期冷冻胚胎移植的1331个周期,包括慢速冷冻周期431个和玻璃化冷冻周期900个,比较两种不同冷冻方法的胚胎复苏率、完整胚胎率、临床妊娠率、种植率、流产率等各项指标,并分析卵裂球损伤对胚胎发育潜能的影响。结果玻璃化冷冻的胚胎复苏率(92.53%)、完整胚胎率(75.43%)、临床妊娠率(45.72%)、种植率(27.41%)高于慢速冷冻(76.93%、48.46%、39.52%、19.88%,P0.05);而流产率分别为12.20%、12.56%(P0.05);周期取消率分别为3.71%、1.33%(P0.05)。慢速冷冻移植0、1、2、3个无卵裂球损伤胚胎的临床妊娠率分别为:36.2%、37.7%、42.0%、44.3%(P0.05);玻璃化冷冻移植0、1、2、3个无卵裂球损伤胚胎的临床妊娠率分别为:20.5%、42.3%、48.8%、54.1%(P0.05)。结论玻璃化冷冻法更适合于人卵裂期胚胎冷冻保存,其冷冻胚胎移植周期的妊娠结局要优于慢速冷冻法;卵裂球损伤对玻璃化冷冻复苏胚胎的发育潜能影响较大。     

早补救ICSI新鲜周期与复苏周期卵裂期胚胎移植临床结局分析

目的探讨行早补救ICSI助孕治疗患者新鲜周期与复苏周期卵裂期胚胎移植的临床妊娠结局。方法回顾性分析2014年01月至2017年06月期间在我院生殖中心接受治疗的患者,在短时受精失败行早补救ICSI助孕、并行冷冻卵裂期胚胎移植的患者共29个周期,为复苏周期组;与同期行早补救ICSI助孕而移植新鲜卵裂期胚胎的患者共16个周期,为新鲜周期组,比较两组的临床妊娠结局。结果复苏周期的临床妊娠率为41.38%(12/29),胚胎种植率为33.33%(18/54),流产率为16.67%(2/12);新鲜周期的临床妊娠率为43.75%(7/16),胚胎种植率为34.48%(10/29),流产率为14.28%(1/7),两组之间临床妊娠率、种植率及流产率差异均无统计学意义(P0.05)。结论早补救ICSI助孕治疗患者行新鲜周期与复苏周期的卵裂期胚胎均可获得较好的临床妊娠结局,早补救ICSI不失为一种有效的辅助生殖补救措施,改善了部分患者临床治疗结局。     

不同发育时期的冻融胚胎移植的成功率分析

目的探讨辅助生殖技术中,胚胎冷冻时的发育阶段对冻融胚胎移植的成功率的影响.方法回顾性分析107个冻融胚胎移植周期.结果胚胎复苏率为57.2%(271/474),临床妊娠率为27.1% (29/107),种植率为15.1% (39/259).按胚胎冷冻时期不同分为受精后第二天组(2～6细胞)和第三天组(4～10细胞),Day 3组的胚胎存活率显著高于Day 2组,但完整胚胎存活率、妊娠率、种植率均无显著性差异(P＞0.05).妊娠组的完整胚胎存活率及移植胚胎数目明显高于未妊娠组(P＜0.05).两组的子宫内膜的厚度和分型差异无显著性.结论在受精后第二天或第三天冷冻的胚胎,复苏后胚胎移植的妊娠率、种植率均无显著性差异.冻融胚胎形态良好,有足够的移植胚胎数目是保证冻融胚胎移植成功的重要因素.     

胚胎早期卵裂观察在胚胎发育潜能评估中的应用分析

目的探讨取卵后第一天(Day1)胚胎早期卵裂的观察在胚胎发育潜能及临床妊娠结局的预测价值。方法分析2013年5月至2014年4月179个常规IVF周期,依据受精后28±1h双原核(2pn)受精卵早期卵裂情况,分为早期卵裂组(A组)、pn消失未早期卵裂组(B组)、pn未消失未早期卵裂组(C组),比较每组优质胚胎率、可利用囊胚形成率和临床妊娠率等,其中移植结局又根据移植胚胎来源分4组,a组全移植早期卵裂来源胚胎、b组1个为早期卵裂来源胚胎、c组为pn消失未早期卵裂来源胚胎、d组为pn未消失未早期卵裂来源胚胎。结果 1.Day3评分A组、B组、C组的优质胚胎率(61.3%vs 53.1%vs32.1%),差异有统计学意义(P0.05);胚胎可利用率为(72.2%vs 65.5%vs 39.1%),差异有统计学意义(P0.05);可利用囊胚形成率(41.6%vs 37.9%vs 22.2%),差异有统计学意义(P0.05)。2.早期卵裂细胞数为2且评分≤2级的胚胎形成优质胚胎率、可利用囊胚形成率均高于早期卵裂细胞数≥3或评分≥3级的胚胎,差异有统计学意义(P0.05)。3.移植a组、b组、c组、d组的临床妊娠率为63.5%、48.3%、50.0%、44.6%,移植a组的临床妊娠率明显高于其它组别,但差异无统计学意义(P0.05)。结论早期卵裂组的优质胚胎率、可利用囊胚形成率及胚胎移植结局明显高于非早期卵裂组,提示胚胎早期卵裂的观察有助于预测胚胎发育潜能,而早期卵裂细胞数为2且评分≤2级的胚胎发育潜能高。     

Teratozoospermia influences fertilization rate in vitro but not embryo quality

The purpose of this study was to retrospectively compare the overall results and embryo quality in 102 cycles of in-vitro fertilization (IVF)-embryo transfer using normal frozen donor semen (group D) and 94 cycles of IVF-embryo transfer using husbands' teratozoospermic sperm (group T). Donor semen was purchased from men with proven fertility and normal semen parameters. Teratozoospermia was defined in group T as the presence of <20% of normal spermatozoa in semen on the day of oocyte retrieval. Exclusion criteria were a sperm count <10 x 10(6)/ml or with <10% progressive motility. Fertilization rate, transfer rate and number of transferred embryos per cycle were significantly lower in the teratozoospermic group (45 vs 72%, 66 vs 96%, 1.7 vs 2.9%, respectively). Pregnancy rate per cycle was also lower, but not significantly (18 vs 28%). However, pregnancy rate per transfer, implantation rate per transferred embryo and take home baby rate were comparable (27 vs 30%, 15 vs 15%, 21 vs 24%, respectively). Similarly, embryo quality in terms of number of embryos displaying fragmentations or irregular cells, cleavage stages and embryo scores were comparable. When group T was divided into two subgroups according to sperm count (group T1: sperm count = 10-20 x 10(6)/ml; group T2: sperm count >20 x 10(6)/ml), there was no difference between them with regard to fertilization rate, pregnancy rate or embryo quality. This study confirms low pregnancy rate per cycle in IVF-embryo transfer using teratozoospermic semen, but demonstrates for the first time that embryo quality and viability are not impaired. It is proposed that the poor pregnancy rate per cycle obtained is due only to the poor fertilization rate, and to the subsequent limited choice of embryos to be transferred.      

The window for embryo transfer in oocyte donation cycles depends on the duration of progesterone therapy

In 192 oocyte donation cycles performed between January 1993 and July 1996, we examined the width of 'the window for embryo transfer' using standard hormonal replacement methods. All transfers were performed within 48 h of insemination. We varied the day of embryo transfer with regard to the initiation of progesterone therapy and, thus, the duration of endometrial exposure to progesterone and analysed the resulting pregnancy rates. Patients were divided into five groups (I-V) and embryo transfers were performed 2, 3, 4, 5 or 6 days following initiation of progesterone therapy. The number of pregnancies per transfer cycle achieved in groups I-V were 0 (0%), 3 (12%), 16 (40%), 29 (48.3%), and 10 (20.4%) respectively. The increased pregnancy rate in group III in comparison to group II is statistically significant (P < 0.03). Furthermore, the pregnancy rate in group IV (5 days of progesterone administration before embryo transfer) was significantly higher than in group V (6 days of progesterone administration before embryo transfer; P < 0.005). We also noted that, when embryos were transferred 4 or 5 days after initiation of progesterone therapy, the pregnancy rates were not significantly different between menopausal and cycling recipients (50% vs 43.7%). Our results indicate that the window for embryo transfer is dependent on duration of treatment with progesterone; it begins approximately 48 h after starting progesterone administration and lasts for approximately 4 days. The optimum period for transferring embryos at the 4- to 8-cell stage corresponds to cycle days 18 and 19. Transfers performed on the 17th and 20th days of the cycle can result in successful implantation, although the rates of implantation are highest when transfers are done on days 18 and 19.      

Is there any benefit from the culture of a single oocyte to a blastocyst-stage embryo in unstimulated cycles?

BACKGROUND: The aim of the study was to test the influence of 2- and 5-day cultivation of a single oocyte on the pregnancy rate in a non-stimulated cycle. METHODS: A retrospective chart review of 391 consecutive patients undergoing IVF and intracytoplasmic sperm injection in unstimulated cycles was performed. The embryos were kept in MediCult universal IVF medium for day 2 transfers and in BlastAssist System for day 5 transfers. RESULTS: The oocyte recovery rate in the group for 2-day cultivation and in the group for 5-day cultivation was similar, being 79.4 (162/204) and 83.6% (154/187) respectively. The same is true of the fertilization rate (73.8 versus 77.7%). The blastulation rate was 52.8%. The embryo transfer rate per cycle was higher when day 2 embryos were transferred: 64.8% (105/162) compared with 35.7% (55/154) if blastocyst-stage embryos were transferred. The pregnancy rate per transferred embryo was higher when a blastocyst was transferred (40.0%) instead of a day 2 embryo (23.8%). CONCLUSION: The expected pregnancy rate calculated per embryo available on day 2 of cultivation was similar in both groups (23.8 versus 22.2%) and it was not affected by oocyte culture to the blastocyst stage.     

GnRHa降调节联合人工周期方案在反复植入失败患者中的 应用研究

目的 探讨GnRHa降调节联合人工周期方案对反复植入失败后冻融胚胎移植妊娠结局的影响。方法 对170例胚胎反复植入失败患者的解冻胚胎移植周期进行回顾性分析,根据内膜准备方案的不同分为两组。A组90例GnRHa降调节联合人工周期组,B组80例人工周期组,分别比较两组在黄体酮转化日内膜厚度、类型、血清雌二醇水平以及移植胚胎数、优胚数、优胚率、临床妊娠率、异位妊娠率、多胎率、早期流产率。结果 A组与B组患者在黄体酮转化日内膜的厚度、移植胚胎数、优质胚胎数、优质胚胎率、多胎率、异位妊娠率及早期流产率,差异无统计学意义(P＞0.05);A组患者黄体酮转化日血清雌二醇水平低于B组,差异有统计学意义(P＜0.05);两组患者内膜分型比较,差异无统计学意义(P＞0.05),但降调节联合人工周期组患者A型内膜的比例较人工周期组高;A组患者的临床妊娠率为56.67%高于B组42.50%,差异有统计学意义(P＜0.05)。结论 GnRHa降调节联合人工周期方案可改善反复植入失败后冻融胚胎移植的妊娠率。     

Early cleavage is a valuable addition to existing embryo selection parameters: a study using single embryo transfers

BACKGROUND: To reduce the twin pregnancy rate, elective single embryo transfer (eSET) is increasingly implemented. Improvement of the results obtained with eSET can be achieved by better selection of the most viable embryo. This study investigated the predictive value of early cleavage (EC) as an additional parameter for selecting the embryo with the highest implantation potential by using data from SET's. METHODS: Data from 165 SET's were retrospectively evaluated. Cleavage to the 2-cell stage was determined 23-26 h after injection or 25-28 h after insemination. Selection of the embryo to be transferred was based on cell morphology and cell number on the day of transfer, not on the EC status. Additional information on the predictive value of EC on developmental potential was obtained by analysing 253 transfers with two embryos (double embryo transfer, DET) and blastocyst formation of 1160 surplus embryos. Logistic regression was used to determine the predictors of pregnancy or blastocyst development. RESULTS: A significantly higher pregnancy rate was observed after transfer of single EC embryos compared to single non-EC embryos (46 versus 18%). This result was confirmed by the significantly higher pregnancy rate after DET with two EC embryos as compared to DET with two non-EC embryos (45 versus 25%) and the blastocyst formation of EC embryos compared to non-EC embryos (66 versus 40%). Logistic regression showed that EC is an independent predictor for both pregnancy and blastocyst development in addition to cell morphology and cell number. CONCLUSIONS: In order to improve the selection of the embryo with the highest implantation potential, selection for transfer should not be based on cell number and morphology on the day of transfer alone, but also on early cleavage status.     

影响冻融胚胎临床结局的因素分析

目的探讨影响冻融胚胎移植结局的相关因素。方法收集我中心2009年570个行冻融胚胎移植周期,回顾性分析患者年龄,移植冻融胚胎质量及数量,内膜厚度对临床妊娠率、种植率、多胎率的影响。结果 Logistic回归分析表明:女方年龄、移植数、移植优质胚胎数与临床妊娠显著相关(P<0.01);多胎与女方年龄和移植数相关(P<0.01;P<0.05)。年龄<35岁的妊娠率(49.4%)明显高于≥35岁的妊娠率(37.9%)(P<0.05);移植2个胚胎的临床妊娠率(49.3%),明显高于移植1个胚胎的临床妊娠率(15.4%)(P<0.05),但与移植3个胚胎的临床妊娠率(50.0%)无差异(P>0.05);移植至少1个优胚组妊娠率(58.0%)较无优胚移植组临床妊娠率(37.5%)显著高(P<0.01)。结论女方年龄及移植的胚胎质量是影响移植后妊娠结局的关键因素。     

Blastocyst formation--good indicator of clinical results after ICSI with testicular spermatozoa

BACKGROUND: The aim of this study was to evaluate the role of blastocyst culture in patients with azoospermia. METHODS: In 98 cycles embryos were cultured for 2 days and in 128 cycles for 5 days to reach the blastocyst stage; a maximum of two of the most developed embryos were transferred in each group. RESULTS: There was a negative correlation between a high (>/=20 IU/l) male serum FSH and embryo development, manifested as embryos not reaching the morula stage on day 5 (r = 0.387; P < 0.05). After prolonged culture, 23% of embryos reached the blastocyst stage. The pregnancy rates per transfer, and the abortion rates were approximately the same in the day 2 group and the day 5 group (20 versus 20% and 19 versus 18% respectively). After blastocyst transfer, a high clinical pregnancy rate (55%) and a low abortion rate (6%) were achieved, whereas the transfer of arrested embryos provided a low pregnancy rate (2%) and a high abortion rate (100%). If only blastocysts had been transferred on day 5, the clinical pregnancy rate per started cycle would have been approximately the same in both groups (13 versus 16%). CONCLUSIONS: Blastocyst formation is a good indicator of clinical results after ICSI with testicular sperm.     

Live birth rate is significantly higher after blastocyst transfer than after cleavage-stage embryo transfer when at least four embryos are available on day 3 of embryo culture. A randomized prospective study

INTRODUCTION: In a randomized controlled trial, we assessed whether pregnancy outcome would be improved by extending embryo culture to day 5 and transferring a blastocyst in patients with at least four good-quality embryos on day 3. METHODS: Multifollicular ovarian stimulation was performed with a GnRH agonist in 44% of patients and with a GnRH antagonist in 56%. Overall, 164 patients younger than 37 years fulfilled embryo quality criteria (at least four having at least six cells on the morning of day 3, maximum 20% anucleate fragments) on the third day of culture and were randomized to the day 3 (n = 84) or day 5 (n = 80) groups. Equal numbers of embryos (n = 2) were transferred in each group. RESULTS: Demographics, stimulation parameters and embryological data were comparable in the two groups. Blastocyst-stage transfer resulted in a significantly higher ongoing pregnancy rate [51.3 versus 27.4%; odds ratio (OR) 2.78, 95% confidence interval (CI) 1.45-5.34] and live birth rate (47.5 versus 27.4%; OR 2.40, 95% CI 1.25-4.59) compared with day-3 embryo transfer. A high twin birth rate was observed in both groups (36.8 versus 30.4%; P > 0.05). CONCLUSIONS: A threshold of four good embryos on the third day of embryo culture appears to indicate that the patient will benefit from embryo transfer at the blastocyst stage and have a better chance of achieving a live delivery than with cleavage-stage embryo transfer.     

The neglected morula/compact stage embryo transfer

BACKGROUND: This retrospective study analysed the outcomes of 339 embryo transfers on either day 3 (n = 97) or day 4 (n = 242), and proposed a grading system for morula/compact embryos. METHODS: The morula/compact embryo grading was based on: (i) the proportion of blastomeres undergoing the compaction process; (ii) the morphology of the compacted multicellular mass; (iii) the embryo quality on day 2 and 3; and (iv) the amount of fragmentation. Embryo transfers were classified into groups as follows: group I: transferred with zero 'good' embryos; group II: one 'good' embryo; group III: two or more 'good' embryos. RESULTS: Patients on day 4 were transferred with significantly fewer embryos in groups II and III (2.58 +/- 0.9 and 2.35 +/- 0.6 respectively) when compared with the correspondent day 3 transfers (3.81 +/- 1.4 and 4.07 +/- 0.9 respectively) (P < 0.05), but had the same or higher implantation and pregnancy rates. Analysing the patients who had transfers with all 'good' embryos, day 4 transfer achieved a significantly higher implantation rate compared with day 3 transfer (46.4 versus 21.4%, P < 0.01), but the number of embryos transferred on day 4 was significantly lower than day 3 (2.1 +/- 0.5 versus 3.5 +/- 0.9, P < 0.01). CONCLUSIONS: The morula/compact embryos had great value for embryo selection, which significantly reduced the number of embryos needed for transfer.     

Parameters guiding selection of best embryos for transfer after cryopreservation: a reappraisal

BACKGROUND: The purpose of this study was to evaluate the respective influences of blastomere survival and resumption of mitosis on the outcome of frozen-thawed embryos. METHODS: A retrospective analysis was performed in our centre on 363 thawing cycles, involving 4-cell day 2 grade 1 embryos with <10% fragmentation. RESULTS: A higher implantation rate per transferred embryo was observed when all transferred embryos were characterized by fully intact blastomeres (100% blastomere survival) as compared with damaged embryos (50 or 75% blastomere survival) (22.0 versus 7.2%; P < 0.0001). Moreover, the implantation rate per transferred embryo was significantly higher for cleaved embryos compared with uncleaved embryos (19.7 versus 3%; P < 0.0001). Transfer of fully intact, cleaved embryos resulted in the highest implantation rates compared with transfer of damaged and uncleaved embryos (27.4 versus 0%; P < 0.0001). Intermediate implantation rates were observed when only one of the two criteria was fulfilled (13 versus 11% respectively; P > 0.05). Multivariate analysis showed that the clinical pregnancy rate was influenced by both criteria (odds ratio = 3.4 for transfer of embryos with six or more cells versus embryos with less than six cells. CONCLUSION: The results of our study suggest that the most important factor to predict further embryo development is the total number of blastomeres in transferred embryos, however they are obtained (good survival and/or resumption of mitosis).