Morphologic parameters of early cleavage-stage embryos that correlate with fetal development and delivery: prospective and applied data for increased pregnancy rates

Hum Reprod. 2007 Jan;22(1):230-40. doi: 10.1093/humrep/del358. Epub 2006 Sep 18.


Background: Many different embryo selection criteria have been used in assisted reproductive technologies (ART), but there are no published prospective studies to ascertain their usefulness in predicting implantation.

Methods: In a prospective trial, 20 early scoring parameters previously reported to influence clinical outcome were collected, but embryos were selected for transfer by current laboratory protocols; day 1 pronuclear (PN) (Z) score combined with day 3 or 5 morphology. Data points for each oocyte/embryo were scored independently and tracked individually. Data were analysed retrospectively for parameters most likely to result in a positive pregnancy test, fetal heartbeat (FHB) and delivery.

Results: Results indicated that day 1 PN morphology and nucleolar precursor body (NPB) ratio, day 2 cell number, blastomere symmetry and nucleation and the ability to cleave from day 2 to day 3 were the six most significant factors in fetal development. This outcome was then applied prospectively over 8 months. The implantation rate (IR) and clinical pregnancy rate (CPR) increased in each age group, and the number of embryos used decreased.

Conclusion: In conclusion, early parameters that include PN morphology, number and ratio of NPBs per nucleus and the day 2 morphology of cleaving embryos are stronger positive predictors of implantation than day 3 morphology or the ability to achieve the blastocyst stage of development. Parameters that were most consistently correlated with no delivery were lack of PN symmetry, day 2 multinucleation and uneven cell size. Day 3 and day 5 parameters were not significant compared with the combination of early parameters.

Publication types

  • Validation Study

MeSH terms

  • Adult
  • Delivery, Obstetric
  • Embryo Implantation
  • Embryo Transfer*
  • Embryo, Mammalian / ultrastructure
  • Female
  • Fetal Development / physiology*
  • Humans
  • Oocytes / cytology
  • Pregnancy
  • Pregnancy Rate
  • Prospective Studies