Cleavage kinetics analysis of human embryos predicts development to blastocyst and implantation

Abstract

Cleavage kinetics of human embryos is indicative of ability to develop to blastocyst and implant. Recent advances in time-lapse microscopy have opened new and important research opportunities. In this study involving infertile couples requiring standard IVF/intracytoplasmic sperm injection treatment, zygotes were cultured by integrated embryo-culture time-lapse microscopy to analyse cleavage times from the 2- to the 8-cell stages in relation to the ability to develop to blastocyst, expand and implant. In comparison to embryos arresting after 8-cell stage, times of cleavage to 7- and 8-cell stages of embryos developing to blastocyst were shorter (56.5 ± 8.1 versus 58.8 ± 10.4h, P=0.03 and 61.0 ± 9.4 versus 65.2 ± 13.0 h, P=0.0008, respectively). In embryos developing to blastocyst, absence of blastocoele expansion on day 5 was associated with progressive cleavage delay. Implanting embryos developed to 8-cell stage in a shorter period compared with those unable to implant (54.9 ± 5.2 and 58.0 ± 7.2h, respectively, P=0.035). In conclusion, cleavage from 2- to 8-cell stage occurs progressively earlier in embryos with the ability to develop to blastocyst, expand and implant. Conventional observation times on days 2 and 3 are inappropriate for accurate embryo evaluation. The speed at which human embryos cleave is known to be suggestive of their ability to develop in vitro to the blastocyst stage and implant after transfer into the uterus. Recent advances in time-lapse microscopy, which allows acquisition of images every 15-20 min, have opened new and important research opportunities. In a retrospective study involving infertile couples requiring standard IVF or intracytoplasmic sperm injection treatment, fertilized oocytes were cultured by an integrated embryo-culture time-lapse microscopy system in order to perform an analysis of cleavage times from the 2- to the 8-cell stage in relation to the ability to develop to blastocyst, expand and implant. In comparison to embryos arresting after the 8-cell stage, times of cleavage to the 7- and 8-cell stage of embryos that developed to blastocyst were significantly shorter (56.5 ± 8.1h versus 58.8 ± 10.4h and 61.0 ± 9.4h versus 65.2 ± 13.0 h, respectively). In embryos developing to the blastocyst stage, absence of blastocoele expansion on day 5 was associated with a progressive cleavage delay. Implanting embryos developed to the 8-cell stage in a shorter period compared to those unable to implant (54.9 ± 5.2h and 58.0 ± 7.2h, respectively, P=0.035). In conclusion, cleavage from the 2- to the 8-cell stage occurs progressively earlier in embryos with the ability to develop to blastocyst, expand and implant. Conventional observation times on day 2 and 3 are appropriate for accurate embryo evaluation.