Extended culture of cleavage-stage embryos in vitrified–thawed cycles may be an alternative to frozen and thawed blastocysts during in vitro fertilization

Abstract

Aim

We compared the clinical outcomes of vitrified–thawed cycles during in vitro fertilization (IVF) for frozen and thawed blastocysts compared to cleavage-stage embryos that were frozen, thawed and extended culture to the blastocyst stage.

Material and methods

Between January 2014 and December 2016, 908 frozen-thawed cycles were included in the study. After removing cycles that met exclusion criteria, clinical outcomes for 355 cleavage-stage embryos with extended blastocyst culture (Group I) were compared with 279 frozen and thawed blastocysts (Group II).

Results

Cryo-survival rate of the two groups were similar (96.7% versus 95.0%). Implantation rates (28.9% versus 22.4%, p = .04) and clinical pregnancy rates (37.2% versus 27.9%, p = .03) were higher in Group I. Pregnancy, live birth and abortus rates were similar in both groups. Although overall abortus rates were similar in both groups, abortus rates before 12 weeks of gestation were higher in Group I, and chemical abortus rates were higher in Group II (p = .03, p = .04). Weeks of gestation at birth and birth weight were similar in both groups.

Conclusions

The use of extended blastocyst culture of cleavage-stage embryos was not inferior to frozen and thawed blastocysts. Freezing at the cleavage-stage can provide similar cryo-survival rates than blastocyst vitrification. Vitrifying surplus or all embryos for storage at the cleavage-stage allows higher implantation and clinical pregnancy rates. But after abortus, live birth rates were similar in both groups.

延长玻璃化冻存周期中卵裂期胚胎的培养可能是体外受精中冻存胚胎的另一种选择 摘要

目的：我们比较了体外受精（IVF）冻存囊胚的玻璃化冻存周期与卵裂期胚胎冻存并延长培养到囊胚期的临床结局。

材料与方法：2014年1月至2016年12月, 共纳入研究908个冻存周期。按照入排标准, 将355个延长至囊胚培养的分裂期胚胎(I组)与279个冻存囊胚(II组)的临床结局进行比较。

结果：两组患者的冷冻存活率相似（96.7%vs95.0%）。I组的植入率(28.9%vs22.4%, p=.04)和临床妊娠率(37.2%vs27.9%, p=.03)较高。两组的妊娠率、活产率和流产率相似。虽然两组的总体流产率相似, 但I组妊娠12周前的流产率较高, II组的化学流产率较高(p=.03, p=.04)。两组患者分娩时的孕周和胎儿出生体重相似。

结论：延长卵裂期胚胎至囊胚培养效果并不低于冷存囊胚的培养。卵裂期冻存能提供与囊胚玻璃化相似的低温存活率。将剩余的胚胎或所有的胚胎玻璃化保存在卵裂期, 可提高植入率和临床妊娠率。但流产率, 活产率相似。

Keywords:

• IVF
• extended culture
• vitrified–thawed
• cleavage stage
• blastocyst

Disclosure statement

No potential conflict of interest was reported by the author(s).